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Education

Education in its general sense is a form of learning in which knowledge, skills, and habits of a group of people are transferred from one generation to the next through teaching, training, research, or simply through autodidacticism.[1] Generally, it occurs through any experience that has a formative effect on the way one thinks, feels, or acts.
Etymology

Etymologically, the word "education" is derived from the Latin ēducātiō (“A breeding, a bringing up, a rearing") from ēdūcō (“I educate, I train”) which is related to the homonym ēdūcō (“I lead forth, I take out; I raise up, I erect”) from ē- (“from, out of”) and dūcō (“I lead, I conduct”).[2]
The role of government

A right to education has been created and recognized by some jurisdictions: Since 1952, Article 2 of the first Protocol to the European Convention on Human Rights obliges all signatory parties to guarantee the right to education. It does not however guarantee any particular level of education of any particular quality.[3] At the global level, the United Nations' International Covenant on Economic, Social and Cultural Rights of 1966 guarantees this right under its Article 13.[4]

Throughout history various governments have made it illegal to educate children privately or at home. Various totalitarian regimes, for example, have mandated indoctrination through propaganda in the Hitler Youth and propaganda in education under various communist regimes.
Systems
Systems of schooling involve institutionalized teaching and learning in relation to a curriculum, which itself is established according to a predetermined purpose of the schools in the system. Schools systems are sometimes also based on religions, giving them different curricula.
Curriculum
Main articles: Curriculum, Curriculum theory, and List of academic disciplines
School children in Durban, South Africa.

In formal education, a curriculum is the set of courses and their content offered at a school or university. As an idea, curriculum stems from the Latin word for race course, referring to the course of deeds and experiences through which children grow to become mature adults. A curriculum is prescriptive, and is based on a more general syllabus which merely specifies what topics must be understood and to what level to achieve a particular grade or standard.

An academic discipline is a branch of knowledge which is formally taught, either at the university–or via some other such method. Each discipline usually has several sub-disciplines or branches, and distinguishing lines are often both arbitrary and ambiguous. Examples of broad areas of academic disciplines include the natural sciences, mathematics, computer science, social sciences, humanities and applied sciences.[5]

Educational institutions may incorporate fine arts as part of K-12 grade curricula or within majors at colleges and universities as electives. The various types of fine arts are music, dance, and theater.[6]
Preschools
Main article: Preschool education

The term preschool refers to a school for children who are not old enough to attend kindergarten. It is a nursery school.

Preschool education is important because it can give a child the edge in a competitive world and education climate.[citation needed] While children who do not receive the fundamentals during their preschool years will be taught the alphabet, counting, shapes and colors and designs when they begin their formal education they will be behind the children who already possess that knowledge. The true purpose behind kindergarten is “to provide a child-centered, preschool curriculum for three to seven year old children that aimed at unfolding the child’s physical, intellectual, and moral nature with balanced emphasis on each of them.”[7]
Primary schools
Main article: Primary education
Primary school in open air. Teacher (priest) with class from the outskirts of Bucharest, around 1842.

Primary (or elementary) education consists of the first 5–7 years of formal, structured education. In general, primary education consists of six or eight years of schooling starting at the age of five or six, although this varies between, and sometimes within, countries. Globally, around 89% of primary-age children are enrolled in primary education, and this proportion is rising.[8] Under the Education For All programs driven by UNESCO, most countries have committed to achieving universal enrollment in primary education by 2015, and in many countries, it is compulsory for children to receive primary education. The division between primary and secondary education is somewhat arbitrary, but it generally occurs at about eleven or twelve years of age. Some education systems have separate middle schools, with the transition to the final stage of secondary education taking place at around the age of fourteen. Schools that provide primary education, are mostly referred to as primary schools. Primary schools in these countries are often subdivided into infant schools and junior school.

In India, compulsory education spans over twelve years, out of which children receive elementary education for 8 years. Elementary schooling consists of five years of primary schooling and 3 years of upper primary schooling. Various states in the republic of India provide 12 years of compulsory school education based on national curriculum framework designed by the National Council of Educational Research and Training.
Secondary schools
Main article: Secondary education
Students working with a teacher at Albany Senior High School, New Zealand
Students in a classroom at Samdach Euv High School, Cambodia

In most contemporary educational systems of the world, secondary education comprises the formal education that occurs during adolescence. It is characterized by transition from the typically compulsory, comprehensive primary education for minors, to the optional, selective tertiary, "post-secondary", or "higher" education (e.g. university, vocational school) for adults. Depending on the system, schools for this period, or a part of it, may be called secondary or high schools, gymnasiums, lyceums, middle schools, colleges, or vocational schools. The exact meaning of any of these terms varies from one system to another. The exact boundary between primary and secondary education also varies from country to country and even within them, but is generally around the seventh to the tenth year of schooling. Secondary education occurs mainly during the teenage years. In the United States, Canada and Australia primary and secondary education together are sometimes referred to as K-12 education, and in New Zealand Year 1–13 is used. The purpose of secondary education can be to give common knowledge, to prepare for higher education or to train directly in a profession.

The emergence of secondary education in the United States did not happen until 1910, caused by the rise in big businesses and technological advances in factories (for instance, the emergence of electrification), that required skilled workers. In order to meet this new job demand, high schools were created, with a curriculum focused on practical job skills that would better prepare students for white collar or skilled blue collar work. This proved to be beneficial for both employers and employees, for the improvement in human capital caused employees to become more efficient, which lowered costs for the employer, and skilled employees received a higher wage than employees with just primary educational attainment.

In Europe, grammar schools or academies date from as early as the 16th century, in the form of public schools, fee-paying schools, or charitable educational foundations, which themselves have an even longer history.
A violin student receiving music education at the Royal Academy of Music, London, 1944.
Autodidacticism
Main article: Autodidacticism

Autodidacticism (also autodidactism) is self-directed learning that is related to but different from informal learning. In a sense, autodidacticism is "learning on your own" or "by yourself", and an autodidact is a self-teacher. Autodidacticism is a contemplative, absorbing process. Some autodidacts spend a great deal of time reviewing the resources of libraries and educational websites. One may become an autodidact at nearly any point in one's life. While some may have been informed in a conventional manner in a particular field, they may choose to inform themselves in other, often unrelated areas. Notable autodidacts include Abraham Lincoln (U.S. president), Srinivasa Ramanujan (mathematician), Michael Faraday (chemist and physicist), Charles Darwin (naturalist), Thomas Alva Edison (inventor), Tadao Ando (architect), George Bernard Shaw (playwright), Frank Zappa (composer, recording engineer, film director),and Leonardo da Vinci (engineer, scientist, mathematician).
Vocational
Main article: Vocational education

Vocational education is a form of education focused on direct and practical training for a specific trade or craft. Vocational education may come in the form of an apprenticeship or internship as well as institutions teaching courses such as carpentry, agriculture, engineering, medicine, architecture and the arts.
Indigenous
Main article: Indigenous education

Indigenous education refers to the inclusion of indigenous knowledge, models, methods and content within formal and non-formal educational systems. Often in a post-colonial context, the growing recognition and use of indigenous education methods can be a response to the erosion and loss of indigenous knowledge and language through the processes of colonialism. Furthermore, it can enable indigenous communities to “reclaim and revalue their languages and cultures, and in so doing, improve the educational success of indigenous students.”[9]
Anarchistic free schools
Main article: Anarchistic free school

An anarchistic free school (also anarchist free school and free school) is a decentralized network in which skills, information, and knowledge are shared without hierarchy or the institutional environment of formal schooling. Free school students may be adults, children, or both. This organisational structure is distinct from ones used by democratic free schools which permit children's individual initiatives and learning endeavors within the context of a school democracy, and from free education where 'traditional' schooling is made available to pupils without charge. The open structure of free schools is intended to encourage self-reliance, critical consciousness, and personal development. Free schools often operate outside the market economy in favor of a gift economy.[citation needed] Nevertheless, the meaning of the "free" of free schools is not restricted to monetary cost, and can refer to an emphasis on free speech and student-centred education.[citation needed]
Alternative
Main article: Alternative education

Alternative education, also known as non-traditional education or educational alternative, is a broad term that may be used to refer to all forms of education outside of traditional education (for all age groups and levels of education). This may include not only forms of education designed for students with special needs (ranging from teenage pregnancy to intellectual disability), but also forms of education designed for a general audience and employing alternative educational philosophies and methods.

Alternatives of the latter type are often the result of education reform and are rooted in various philosophies that are commonly fundamentally different from those of traditional compulsory education. While some have strong political, scholarly, or philosophical orientations, others are more informal associations of teachers and students dissatisfied with certain aspects of traditional education. These alternatives, which include charter schools, alternative schools, independent schools, homeschooling and autodidacticism vary, but often emphasize the value of small class size, close relationships between students and teachers, and a sense of community.

Alternative education may also allow for independent learning and engaging class activities.[10]
Special
Main article: Special education

In the past, those who were disabled were often not eligible for public education. Children with disabilities were often educated by physicians or special tutors. These early physicians (people like Itard, Seguin, Howe, Gallaudet) set the foundation for special education today. They focused on individualized instruction and functional skills. Special education was only provided to people with severe disabilities in its early years, but more recently it has been opened to anyone who has experienced difficulty learning.[11]
Education through recreation

The concept of education through recreation was first applied to childhood development in the 19th century.[12] In the early 20th century, the concept was broadened to include young adults but the emphasis was on physical activities.[13] Educationalist Lawrence L.P. Jacks, who was also an early proponent of lifelong learning, best described the modern concept of education through recreation in the following quotation "A master in the art of living draws no sharp distinction between his work and his play, his labour and his leisure, his mind and his body, his education and his recreation. He hardly knows which is which. He simply pursues his vision of excellence through whatever he is doing and leaves others to determine whether he is working or playing. To himself he always seems to be doing both. Enough for him that he does it well."(Jacks, 1932).[14] Education through recreation is the opportunity to learn in a seamless fashion through all of life's activities.[15] The concept has been revived by the University of Western Ontario to teach anatomy to medical students.[15]
Systems of higher education
Main article: Higher education
The University of Cambridge is an institute of higher learning.

Higher education, also called tertiary, third stage, or post secondary education, is the non-compulsory educational level that follows the completion of a school providing a secondary education, such as a high school or secondary school. Tertiary education is normally taken to include undergraduate and postgraduate education, as well as vocational education and training. Colleges and universities are the main institutions that provide tertiary education. Collectively, these are sometimes known as tertiary institutions. Tertiary education generally results in the receipt of certificates, diplomas, or academic degrees.

Higher education generally involves work towards a degree-level or foundation degree qualification. In most developed countries a high proportion of the population (up to 50%) now enter higher education at some time in their lives. Higher education is therefore very important to national economies, both as a significant industry in its own right, and as a source of trained and educated personnel for the rest of the economy.
University systems
Lecture at the Faculty of Biomedical Engineering, CTU in Prague.

University education includes teaching, research, and social services activities, and it includes both the undergraduate level (sometimes referred to as tertiary education) and the graduate (or postgraduate) level (sometimes referred to as graduate school). Universities are generally composed of several colleges. In the United States, universities can be private and independent, like Yale University, they can be public and State governed, like the Pennsylvania State System of Higher Education, or they can be independent but State funded, like the University of Virginia.
Open

Higher education in particular is currently undergoing a transition towards open education, elearning alone is currently growing at 14x the rate of traditional learning.[16] Open education is fast growing to become the dominant form of education, for many reasons such as its superior efficiency and results compared to traditionalist methods.[17] Cost of education has been an issue throughout history, and a major political issue in most countries today. Open education is generally significantly cheaper than traditional campus based learning and in many cases even free. Many large university institutions are now starting to offer free or almost free full courses such as Harvard, MIT and Berkeley teaming up to form edX Other universities offering open education are Stanford, Princeton, Duke, Johns Hopkins, Edinburgh, U.Penn, U. Michigan, U. Virginia, U. Washington, Caltech. It has been called the biggest change in the way we learn since the printing press.[18] Many people despite favorable studies on effectivness may still desire to choose traditional campus education for social and cultural reasons.[19]

The conventional merit system degree is currently not as common in open education as it is in campus universities. Although some open universities do already offer conventional degrees such as the Open University in the United Kingdom. Currently many of the major open education sources offer their own form of certificate. Due to the popularity of open education these new kind of academic certificates are gaining more respect and equal "academic value" to traditional degrees.[20] Many open universities are working to have the ability to offer students standardized testing and traditional degrees and credentials.[citation needed]

There has been a culture forming around distance learning for people who are looking to enjoy the shared social aspects that many people value in traditional on campus education that is not often directly offered from open education.[citation needed] Examples of this are people in open education forming study groups, meetups and movements such as UnCollege.
Liberal arts colleges
Saint Anselm College, a traditional New England liberal arts college.

A liberal arts institution can be defined as a "college or university curriculum aimed at imparting broad general knowledge and developing general intellectual capacities, in contrast to a professional, vocational, or technical curriculum."[21] Although what is known today as the liberal arts college began in Europe,[22] the term is more commonly associated with Universities in the United States[citation needed].
Community colleges
Main article: community colleges

A nonresidential junior college offering courses to people living in a particular area.
Technology
Main article: Educational technology

One of the most substantial uses in education is the use of technology. Also technology is an increasingly influential factor in education. Computers and mobile phones are used in developed countries both to complement established education practices and develop new ways of learning such as online education (a type of distance education). This gives students the opportunity to choose what they are interested in learning. The proliferation of computers also means the increase of programming and blogging. Technology offers powerful learning tools that demand new skills and understandings of students, including Multimedia, and provides new ways to engage students, such as Virtual learning environments. One such tool are virtual manipulatives, which are an "interactive, Web-based visual representation of a dynamic object that presents opportunities for constructing mathematical knowledge" (Moyer, Bolyard, & Spikell, 2002). In short, virtual manipulatives are dynamic visual/pictorial replicas of physical mathematical manipulatives, which have long been used to demonstrate and teach various mathematical concepts. Virtual manipulatives can be easily accessed on the Internet as stand-alone applets, allowing for easy access and use in a variety of educational settings. Emerging research into the effectiveness of virtual manipulatives as a teaching tool have yielded promising results, suggesting comparable, and in many cases superior overall concept-teaching effectiveness compared to standard teaching methods.[citation needed] Technology is being used more not only in administrative duties in education but also in the instruction of students. The use of technologies such as PowerPoint and interactive whiteboard is capturing the attention of students in the classroom. Technology is also being used in the assessment of students. One example is the Audience Response System (ARS), which allows immediate feedback tests and classroom discussions.[23]
American students in 2001, in a computer fundamentals class taking a computer-based test

Information and communication technologies (ICTs) are a “diverse set of tools and resources used to communicate, create, disseminate, store, and manage information.”[24] These technologies include computers, the Internet, broadcasting technologies (radio and television), and telephony. There is increasing interest in how computers and the Internet can improve education at all levels, in both formal and non-formal settings.[25] Older ICT technologies, such as radio and television, have for over forty years been used for open and distance learning, although print remains the cheapest, most accessible and therefore most dominant delivery mechanism in both developed and developing countries.[26] In addition to classroom application and growth of e-learning opportunities for knowledge attainment, educators involved in student affairs programming have recognized the increasing importance of computer usage with data generation for and about students. Motivation and retention counselors, along with faculty and administrators, can impact the potential academic success of students by provision of technology based experiences in the University setting.[27]

The use of computers and the Internet is in its infancy in developing countries, if these are used at all, due to limited infrastructure and the attendant high costs of access. Usually, various technologies are used in combination rather than as the sole delivery mechanism. For example, the Kothmale Community Radio Internet uses both radio broadcasts and computer and Internet technologies to facilitate the sharing of information and provide educational opportunities in a rural community in Sri Lanka.[28] The Open University of the United Kingdom (UKOU), established in 1969 as the first educational institution in the world wholly dedicated to open and distance learning, still relies heavily on print-based materials supplemented by radio, television and, in recent years, online programming.[29] Similarly, the Indira Gandhi National Open University in India combines the use of print, recorded audio and video, broadcast radio and television, and audio conferencing technologies.[30]

The term "computer-assisted learning" (CAL) has been increasingly used to describe the use of technology in teaching. Classrooms of the 21st century contain interactive white boards, tablets, mp3 players, laptops, etc. Wiki sites are another tool teachers can implement into CAL curricula for students to understand communication and collaboration efforts of group work through electronic means.[citation needed] Teachers are encouraged to embed these technological devices and services in the curriculum in order to enhance students learning and meet the needs of various types of learners.
Adult
Main article: Adult education

Adult learning, or adult education, is the practice of training and developing skills in adults. It is also sometimes referred to as andragogy (the art and science of helping adults learn).Adult education has become common in many countries. It takes on many forms, ranging from formal class-based learning to self-directed learning and e-learning. A number of career specific courses such as veterinary assisting, medical billing and coding, real estate license, bookkeeping and many more are now available to students through the Internet.

With the boom of information from availability of knowledge through means of internet and other modern low cost information exchange mechanisms people are beginning to take an attitude of Lifelong learning. To make knowledge and self improvement a lifelong focus as opposed to the more traditional view that knowledge and in particular value creating trade skills are to be learned just exclusively in youth.
Learning modalities
Students in laboratory, Saint Petersburg State Polytechnical University.

There has been work on learning styles over the last two decades. Dunn and Dunn[31] focused on identifying relevant stimuli that may influence learning and manipulating the school environment, at about the same time as Joseph Renzulli[32] recommended varying teaching strategies. Howard Gardner[33] identified individual talents or aptitudes in his Multiple Intelligences theories. Based on the works of Jung, the Myers-Briggs Type Indicator and Keirsey Temperament Sorter[34] focused on understanding how people's personality affects the way they interact personally, and how this affects the way individuals respond to each other within the learning environment. The work of David Kolb and Anthony Gregorc's Type Delineator[35] follows a similar but more simplified approach.

It is currently fashionable to divide education into different learning "modes". The learning modalities[36] are probably the most common:

    Visual: learning based on observation and seeing what is being learned.
    Auditory: learning based on listening to instructions/information.
    Kinesthetic: learning based on hands-on work and engaging in activities.

Although it is claimed that, depending on their preferred learning modality, different teaching techniques have different levels of effectiveness,[37] recent research has argued "there is no adequate evidence base to justify incorporating learning styles assessments into general educational practice."[38]

A consequence of this theory is that effective teaching should present a variety of teaching methods which cover all three learning modalities so that different students have equal opportunities to learn in a way that is effective for them.[39] Guy Claxton has questioned the extent that learning styles such as VAK are helpful, particularly as they can have a tendency to label children and therefore restrict learning.[40][41]
Instruction
Teacher in a classroom in Madagascar

Instruction is the facilitation of another's learning. Instructors in primary and secondary institutions are often called teachers, and they direct the education of students and might draw on many subjects like reading, writing, mathematics, science and history. Instructors in post-secondary institutions might be called teachers, instructors, or professors, depending on the type of institution; and they primarily teach only their specific discipline. Studies from the United States suggest that the quality of teachers is the single most important factor affecting student performance, and that countries which score highly on international tests have multiple policies in place to ensure that the teachers they employ are as effective as possible.[42][43] With the passing of NCLB in the United States (No Child Left Behind), teachers must be highly qualified. A popular way to gauge teaching performance is to use student evaluations of teachers (SETS), but these evaluations have been criticized for being counterproductive to learning and inaccurate due to student bias.[44]
Theory
Main article: Education theory

Education theory can refer to either a normative or a descriptive theory of education. In the first case, a theory means a postulation about what ought to be. It provides the "goals, norms, and standards for conducting the process of education."[45] In the second case, it means "an hypothesis or set of hypotheses that have been verified by observation and experiment."[46] A descriptive theory of education can be thought of as a conceptual scheme that ties together various "otherwise discrete particulars. . .For example, a cultural theory of education shows how the concept of culture can be used to organize and unify the variety of facts about how and what people learn."[47] Likewise, for example, there is the behaviorist theory of education that comes from educational psychology and the functionalist theory of education that comes from sociology of education.[48]
Economics
Main article: Economics of education
Students on their way to school, Hakha, Chin State, Myanmar

It has been argued that high rates of education are essential for countries to be able to achieve high levels of economic growth.[49] Empirical analyses tend to support the theoretical prediction that poor countries should grow faster than rich countries because they can adopt cutting edge technologies already tried and tested by rich countries. However, technology transfer requires knowledgeable managers and engineers who are able to operate new machines or production practices borrowed from the leader in order to close the gap through imitation. Therefore, a country's ability to learn from the leader is a function of its stock of "human capital". Recent study of the determinants of aggregate economic growth have stressed the importance of fundamental economic institutions[50] and the role of cognitive skills.[51]

At the individual level, there is a large literature, generally related back to the work of Jacob Mincer,[52] on how earnings are related to the schooling and other human capital of the individual. This work has motivated a large number of studies, but is also controversial. The chief controversies revolve around how to interpret the impact of schooling.[53][54]

Economists Samuel Bowles and Herbert Gintis famously argued in 1976 that there was a fundamental conflict in American schooling between the egalitarian goal of democratic participation and the inequalities implied by the continued profitability of capitalist production on the other.

How to make Safe sex

Safe sex is sexual activity engaged in by people who have taken precautions to protect themselves against sexually transmitted infections (STIs) such as HIV/AIDS.[1] It is also referred to as safer sex or protected sex, while unsafe or unprotected sex is sexual activity engaged in without precautions. Some sources prefer the term safer sex to more precisely reflect the fact that these practices reduce, but do not completely eliminate, the risk of disease transmission.[2] In recent years, the term "sexually transmitted infections" (STIs) has been preferred over "STDs", as it has a broader range of meaning; a person may be infected, and may potentially infect others, without showing signs of disease.

Safe sex practices became more prominent in the late 1980s as a result of the AIDS epidemic. Promoting safe sex is now one of the aims of sex education. Safe sex is regarded as a harm reduction strategy aimed at reducing risks.[3][4] The risk reduction of safe sex is not absolute; for example the reduced risk to the receptive partner of acquiring HIV from HIV seropositive partners not wearing condoms to compared to when they wear them is estimated to be about a four- to fivefold.[5] Although some safe sex practices can be used as contraception, most forms of contraception do not protect against all or any STIs; likewise, some safe sex practices, like partner selection and low risk sex behavior, are not effective forms of contraception.

Safe sex is effective on avoiding STDs if only both parties involved in sexual intercourse agreed on doing so and stick to it. During sexual intercourse using condoms, for example, the male might intentionally pull off the condom and continue penetrating without the female (or male receptive partner)'s consent and notice. This is a high risk behavior that betrays trust as well as spreading the disease.
The term safer sex in Canada and the United States has gained greater use by health workers, reflecting that risk of transmission of sexually transmitted infections in various sexual activities is a continuum. The term safe sex is still in common use in the United Kingdom and Australia.[citation needed]

Although "safe sex" is used by individuals to refer to protection against both pregnancy and HIV/AIDS or other STI transmissions, the term was primarily derived in response to the HIV/AIDS epidemic. It is believed that the term of "safe sex" was used in the professional literature in 1984, in the content of a paper on the psychological effect that HIV/AIDS may have on homosexual men. The term was related with the need to develop educational programs for the group considered at risk, homosexual men. A year later, the same term appeared in an article in the New York Times. This article emphasized that most specialists advised their AIDS patients to practice safe sex. The concept included limiting the number of sexual partners, using prophylactics, avoiding bodily fluid exchange, and resisting the use of drugs that reduced inhibitions for high-risk sexual behavior.[6] Moreover, in 1985, the first safe sex guidelines were established by the 'Coalition for Sexual Responsibilities'.[who?] According to these guidelines, safe sex was practiced by using condoms also when engaging in anal or oral sex.[citation needed]

Although this term was primarily used in conjunction with the homosexual male population, in 1986 the concept was spread to the general population. Various programs were developed with the aim of promoting safe sex practices among college students. These programs were focused on promoting the use of the condom, a better knowledge about the partner's sexual history and limiting the number of sexual partners. The first book on this subject appeared in the same year. The book was entitled "Safe Sex in the Age of AIDS", it had 88 pages and it described both positive and negative approaches to the sexual life.[citation needed] Sexual behavior could be either safe (kissing, hugging, massage, body-to-body rubbing, mutual masturbation, exhibitionism and voyeurism, telephone sex, sado-masochism without bruising or bleeding, and use of separate sex toys); possibly safe (use of condoms); and unsafe.[6]

In 1997, specialists in this matter promoted the use of condoms as the most accessible safe sex method (besides abstinence) and they called for TV commercials featuring condoms. During the same year, the Catholic Church in the United States issued their own "safer sex" guidelines on which condoms were listed, though two years later the Vatican urged chastity and heterosexual marriage, attacking the American Catholic bishops' guidelines.

A study carried out in 2006 by Californian specialists showed that the most common definitions of safe sex are condom use (68% of the interviewed subjects), abstinence (31.1% of the interviewed subjects), monogamy (28.4% of the interviewed subjects) and safe partner (18.7% of the interviewed subjects).[6]

"Safer sex" is thought to be a more aggressive term which may make it more obvious to individuals that any type of sexual activity carries a certain degree of risk.

The term "safe love" has also been used, notably by the French Sidaction in the promotion of men's underpants incorporating a condom pocket and including the red ribbon symbol in the design, which were sold to support the charity.
Safe sex precautions
Shunga print by Kunisada depicting masturbation
Avoiding physical contact

Known as autoeroticism, solitary sexual activity is relatively safe. Masturbation, the simple act of stimulating one's own genitalia, is safe so long as contact is not made with other people's bodily fluids. Some activities, such as phone sex and cybersex, that allow for partners to engage in sexual activity without being in the same room, eliminate the risks involved with exchanging bodily fluids.[7]
Non-penetrative sex
Watercolor of manual stimulation of the penis, Johann Nepomuk Geiger, 1840.
Main article: Non-penetrative sex

A range of sex acts, sometimes called "outercourse", can be enjoyed with significantly reduced risks of infection or pregnancy. U.S. President Bill Clinton's surgeon general, Dr. Joycelyn Elders, tried to encourage the use of these practices among young people, but her position encountered opposition from a number of outlets, including the White House itself, and resulted in her being fired by President Clinton in December 1994.[8][9][10]

Non-penetrative sex includes practices such as kissing, mutual masturbation, rubbing or stroking and, according to the Health Department of Western Australia, this sexual practice may prevent pregnancy and most STIs. However, non-penetrative sex may not protect against infections that can be transmitted skin-to-skin such as herpes and genital warts.[citation needed]
Barrier protection

Various protective devices are used to avoid contact with blood, vaginal fluid, semen or other contaminant agents (like skin, hair and shared objects) during sexual activity. Sexual activity using these devices is called protected sex.
Condom machine

    Condoms cover the penis during sexual activity. They are most frequently made of latex, and can also be made out of synthetic materials including polyurethane.
    Female condoms are inserted into the vagina prior to intercourse.
    A dental dam (originally used in dentistry) is a sheet of latex used for protection when engaging in oral sex. It is typically used as a barrier between the mouth and the vulva during cunnilingus or between the mouth and the anus during anal–oral sex.
    Medical gloves made out of latex, vinyl, nitrile, or polyurethane may be used as a makeshift dental dam during oral sex, or to protect the hands during sexual stimulation, such as masturbation. Hands may have invisible cuts on them that may admit pathogens or contaminate the other body part or partner.
    Another way to protect against pathogen transmission is the use of protected or properly cleaned dildos and other sex toys. If a sex toy is to be used in more than one orifice or partner, a condom can be used over it and changed when the toy is moved.

When latex barriers are used, oil-based lubrication can break down the structure of the latex and remove the protection it provides.

Condoms (male or female) are used to protect against STIs, and used with other forms of contraception to improve contraceptive effectiveness. For example, simultaneously using both the male condom and spermicide (applied separately, not pre-lubricated) is believed to reduce perfect-use pregnancy rates to those seen among implant users.[11] However, if two condoms are used simultaneously (male condom on top of male condom, or male condom inside female condom), this increases the chance of condom failure.[12][13]

Proper use of barriers, such as condoms, depends on the cleanliness of surfaces of the barrier, handling can pass contamination to and from surfaces of the barrier unless care is taken.

Studies of latex condom performance during use reported breakage and slippage rates varying from 1.46% to 18.60%.[14] Condoms must be put on before any bodily fluid could be exchanged, and they must be used also during oral sex.[15]

Female condoms are made of two flexible polyurethane rings and a loose-fitting polyurethane sheath.[14] According to laboratory testing, female condoms are effective in preventing the leakage of body fluids and therefore the transmission of STIs and HIV. Several studies show that between 50% and 73% of women who have used this type of condoms during intercourse find them as or more comfortable than male condoms. On the other hand, acceptability of these condoms among the male population is somewhat less, at approximately 40%. Because the cost of female condoms is higher than male condoms, there have been studies carried out with the aim of detecting whether they can be reused. Research has shown that structural integrity of polyurethane female condoms is not damaged during up to five uses if it is disinfected with water and household bleach. However, regardless of this study, specialists still recommend that female condoms are used only once and then discarded.
Other precautions

Acknowledging that it is usually impossible to have entirely risk-free sex with another person, proponents of safe sex recommend that some of the following methods be used to minimize the risks of STI transmission and unwanted pregnancy.

    Immunization against various viral infections that can be transmitted sexually. The most common vaccines are HPV vaccine, which protects against the most common types of human papillomavirus that cause cervical cancer, and the Hepatitis B vaccine. Immunization before initiation of sexual activity increases effectiveness.
    Male circumcision and HIV: Some research has suggested that male circumcision can reduce the risk of HIV infection in some countries. The World Health Organization cites the procedure as a measure against the transmission of HIV between women and men; some African studies have found that circumcision can reduce the rate of transmission of HIV to men by up to 60%.[16] Some advocacy groups dispute these findings.[17][18] In sub-Saharan Africa, at least, condom use and behavior change programs are estimated to be more efficient and much more cost-effective than surgical procedures such as circumcision.[19]
    Periodic STI testing has been used to reduce STIs in Cuba and among pornographic film actors. Cuba implemented a program of mandatory testing and quarantine early in the AIDS epidemic.[20] In the US pornographic film industry, many production companies will not hire actors without tests for Chlamydia, HIV and Gonorrhea that are no more than 30 days old-and tests for other STIs no more than 6 months old. AIM Medical foundation claims that program of testing has reduced the incidence of sexually transmitted infection to 20% of that of the general population.[21] Douching with soap and water disrupts the vaginal flora it might increase risk of infection.[22][23]
    Monogamy or polyfidelity, practiced faithfully, is very safe (as far as STIs are concerned) when all partners are non-infected. However, many monogamous people have been infected with sexually transmitted diseases by partners who are sexually unfaithful, have used injection drugs, or were infected by previous sexual partners; the same risks apply to polyfidelitous people, who face higher risks depending on how many people are in the polyfidelitous group.
    For those who are not monogamous, reducing the number of one's sexual partners, particularly anonymous sexual partners, may also reduce one's potential exposure to STIs. Similarly, one may restrict one's sexual contact to a community of trusted individuals—this is the approach taken by some pornographic actors and other non-monogamous people.
    When selecting a sexual partner, some characteristics can increase the risks for contracting sexually transmitted diseases.[24] These include an age discordance of more than five years;[24] having an STI in the past year;[24] problems with alcohol;[24] having had sex with other people in the past year.[24]
    Communication with one's sexual partner(s) makes for greater safety. Before initiating sexual activities, partners may discuss what activities they will and will not engage in, and what precautions they will take. This can reduce the chance of risky decisions being made "in the heat of passion".
    If a person is sexually active with a number of partners, regular sexual health check-ups by a doctor, and on noticing unusual symptoms seeking prompt medical advice; HIV and other infectious agents can be either asymptomatic or involve nonspecific symptoms which on their own can be misdiagnosed.[25][26]

Limitations

While the use of condoms can reduce transmission of HIV and other infectious agents, it does not do so completely. One study has suggested condoms might reduce HIV transmission by 85% to 95%; effectiveness beyond 95% was deemed unlikely because of slippage, breakage, and incorrect use.[27] It also said, "In practice, inconsistent use may reduce the overall effectiveness of condoms to as low as 60–70%".[27]p. 40.

During each act of anal intercourse, the risk of the receptive partner acquiring HIV from HIV seropositive partners not using condoms is about 1 in 120. Among people using condoms, the receptive partner's risk declines to 1 in 550, a four- to fivefold reduction.[5] Where the partner's HIV status is unknown, "Estimated per-contact risk of protected receptive anal intercourse with HIV-positive and unknown serostatus partners, including episodes in which condoms failed, was two thirds the risk of unprotected receptive anal intercourse with the comparable set of partners."[5]p. 310.
Ineffective methods

Most methods of contraception, except for certain forms of "outercourse" and the barrier methods, are not effective at preventing the spread of STIs. This includes the birth control pills, vasectomy, tubal ligation, periodic abstinence and all non-barrier methods of pregnancy prevention.

The spermicide Nonoxynol-9 has been claimed to reduce the likelihood of STI transmission. However, a recent study by the World Health Organization [28] has shown that Nonoxynol-9 is an irritant and can produce tiny tears in mucous membranes, which may increase the risk of transmission by offering pathogens more easy points of entry into the system. Condoms with Nonoxynol-9 lubricant do not have enough spermicide to increase contraceptive effectiveness and are not to be promoted.[citation needed]

The use of diaphragm or contraceptive sponge provides some women with better protection against certain sexually transmitted diseases,[29] but they are not effective for all STIs.

The hormonal protecting methods are by no means effective against transmission of STIs, even though they are more than 95% effective against unwanted pregnancies. Most common hormonal methods are the oral contraceptive pill, depoprogesterone, the vaginal ring and the patch.

The copper intrauterine device and the hormonal intrauterine device provide an up to 99% protection against pregnancies but no protection against STIs. Women with copper intrauterine device present however a greater risk of being exposed to any type of STI, especially gonorrhea or chlamydia.[citation needed]

Coitus interruptus (or "pulling out"), in which the penis is removed from the vagina, anus, or mouth before ejaculation, is not safe sex and can result in STI transmission. This is because of the formation of pre-ejaculate, a fluid that oozes from the urethra before actual ejaculation, may contain pathogens such as HIV.[30][31] Additionally, the microbes responsible for some diseases, including genital warts and syphilis, can be transmitted through skin-to-skin contact, even if the partners never engage in oral, vaginal, or anal sexual intercourse.
Abstinence

Sexual abstinence is sometimes promoted as a way to avoid the risks associated with sexual contact, though STIs may also be transmitted through non-sexual means, or by involuntary sex. HIV may be transmitted through contaminated needles used in tattooing, body piercing, or injections. Medical or dental procedures using contaminated instruments can also spread HIV, while some health-care workers have acquired HIV through occupational exposure to accidental injuries with needles.[32] Evidence does not support the use of abstinence only sex education.[33] Abstinence-only education programs have been found to be ineffective in decreasing rates of HIV infection in the developed world[34] and unplanned pregnancy.[33]

Some groups, such as some Christian denominations, oppose sex outside marriage and therefore object to safe-sex education programs because they believe that providing such education promotes promiscuity. Virginity pledges and sexual abstinence education programs are often promoted in lieu of contraceptives and safe-sex education programs. This may entail exposing some teenagers to increased risk of sexually transmitted infections, because about 60 percent of teenagers who pledge virginity until marriage do engage in pre-marital sex and are then one-third less likely to use contraceptives than their peers who have received more conventional sex education.[35]
Anal sex

Unprotected anal penetration is a high risk activity, regardless of sexual orientation. Anal sex is a higher risk activity than vaginal intercourse because the thin tissues of the anus and rectum can be easily damaged.[36][37] Slight injuries can allow the passage of bacteria and viruses, including HIV. This includes by the use of anal toys. Condoms may be more likely to break during anal sex than during vaginal sex, increasing the risk.[38]

Anal sex is practiced by many heterosexuals, as well as homosexual couples. The anal area has many erotic nerve endings in both men and women. Because of this, many couples (heterosexual or homosexual) can derive pleasure from some form of 'bottom stimulation'.[36] Safety measures are required also when anal sex occurs between heterosexual partners. Apart from the STI transmission risks, other risks such as infection are high regarding anal intercourse. The main risks which individuals are exposed to when performing anal sex are the transmission of HIV, Hepatitis C and A and Escherichia coli and HPV.[citation needed]

Some researchers suggest that although gay men are more likely to engage in anal sex, heterosexual couples are more likely not to use condoms when doing so.[39] Other researchers state that gay men are not necessarily more likely to engage in anal sex than heterosexual couples.[36]
Precautions

Anal sex should be avoided by couples in which one of the partners has been diagnosed with an STI until the treatment has proven to be effective.

In order to make anal sex safer, the couple must ensure that the anal area is clean and the bowel empty and the partner on whom anal penetration occurs should be able to relax. Regardless of whether anal penetration occurs by using a finger or the penis, the condom is the best barrier method to prevent transmission of STI.

Since the rectum can be easily damaged, the use of lubricants is highly recommended even when penetration occurs by using the finger. Especially for beginners, using a condom on the finger is both a protection measure against STI and a lubricant source. Most condoms are lubricated and they allow less painful and easier penetration. Oil-based lubricants damage latex and should not be used with condoms;[40] water-based and silicone-based lubricants are available instead. Non-latex condoms are available for people who are allergic to latex (e.g., polyurethane condoms that are compatible with both oil-based and water-based lubricants).[citation needed] The "female condom" may also be used effectively by the anal receiving partner.

Anal stimulation with a sex toy requires similar safety measures to anal penetration with a penis, in this case using a condom on the sex toy in a similar way.

It is important that the man washes and cleans his penis after anal intercourse if he intends to penetrate the vagina. Bacteria from the rectum are easily transferred to the vagina, which may cause vaginal infections.[41]

When anal-oral contact occurs, protection is required since this is a risky sexual behavior in which illnesses as Hepatitis A or STIs can be easily transmitted, as well as enteric infections. The dental dam or the plastic wrap[citation needed] are effective protection means whenever anilingus is performed.
Sex toys

Putting a condom on a sex toy provides better sexual hygiene and can help to prevent transmission of infections if the sex toy is shared, provided the condom is replaced when used by a different partner. Some sex toys are made of porous materials, and pores retain viruses and bacteria, which makes it necessary to clean sex toys thoroughly, preferably with use of cleaners specifically for sex toys. Glass sex toys are non-porous and more easily sterilized between uses.[citation needed]

In cases in which one of the partners is treated for an STI, it is recommended that the couple will not use sex toys until the treatment has proved to be effective.

All sex toys have to be properly cleaned after use. The way in which a sex toy is cleaned varies on the type of material it is made of. Some sex toys can be boiled or cleaned in a dishwasher. Most of the sex toys come with advice on the best way to clean and store them and these instructions should be carefully followed.[42] A sex toy should be cleaned not only when it is shared with other individuals but also when it is used on different parts of the body (such as mouth, vagina or anus).

A sex toy should regularly be checked for scratches or breaks that can be breeding ground for bacteria. It is best if the damaged sex toy is replaced by a new undamaged one. Even more hygiene protection should be considered by pregnant women when using sex toys. Sharing any type of sex toy that may draw blood, like whips or needles, is not recommended, and is not safe.[citation needed]

The best way to prevent being infected or infecting someone with an STI is by using protection during sexual intercourse.

Sexual reproduction

Sexual reproduction is a process that creates a new organism by combining the genetic material of two organisms; it occurs both in eukaryotes[1][2] and in prokaryotes.[3] A key similarity between bacterial sex and eukaryotic sex is that DNA originating from two different individuals (parents) join up so that homologous sequences are aligned with each other, and this is followed by exchange of genetic information (a process called genetic recombination). After the new recombinant chromosome is formed it is passed on to progeny).

On the other hand, bacterial conjugation, a type of transfer of DNA between two bacteria, is often mistakenly confused with sexual reproduction,[4] because the mechanics are similar. However, bacterial conjugation is controlled by plasmid genes that are adapted for spreading copies of the plasmid between bacteria. The infrequent integration of a plasmid into a host bacterial chromosome, and the subsequent transfer of a part of the host chromosome to another cell do not appear to be bacterial adaptations.[3][5]

In contrast, bacterial transformation can be regarded as a form of sex in bacteria.[3][6] Bacterial transformation is a complex process encoded by numerous bacterial genes, and is clearly a bacterial adaptation for DNA transfer. This process occurs naturally in at least 40 bacterial species.[7] For a bacterium to bind, take up, and recombine exogenous DNA into its chromosome, it must enter a special physiological state referred to as competence (see Natural competence). Sexual reproduction in early single-celled eukaryotes may have evolved from bacterial transformation.[8]

There are two main processes during sexual reproduction in eukaryotes: meiosis, involving the halving of the number of chromosomes; and fertilization, involving the fusion of two gametes and the restoration of the original number of chromosomes. During meiosis, the chromosomes of each pair usually cross over to achieve homologous recombination.

Sexual reproduction is the primary method of reproduction for the vast majority of macroscopic organisms, including almost all animals and plants. The evolution of sexual reproduction is a major puzzle (see Evolution of sexual reproduction). The first fossilized evidence of sexual reproduction in organisms such as eukaryotes is in the Stenian period, about 1 to 1.2 billion years ago.[9]

Evolutionary thought proposes several explanations for why sexual reproduction developed and why it is maintained. These reasons include fighting the accumulation of deleterious mutations, increasing rate of adaptation to changing environments[10] (see the red queen hypothesis), dealing with competition (see the tangled bank hypothesis) or as an adaptation for repairing DNA damage (see Evolution of sexual reproduction).[3][6][8] The maintenance of sexual reproduction has been explained by theories that work at several different levels of selection, though some of these models remain controversial. New models presented in recent years, however, suggest a basic advantage for sexual reproduction in slowly reproducing, complex organisms, exhibiting characteristics that depend on the specific environment that the given species inhabit, and the particular survival strategies that they employ.
Animals typically produce male gametes called sperm, and female gametes called eggs and ova, following immediately after meiosis, with the gametes produced directly by meiosis. Plants on the other hand have mitosis occurring in spores, which are produced by meiosis. The spores germinate into the gametophyte phase. The gametophytes of different groups of plants vary in size; angiosperms have as few as three cells in pollen, and mosses and other so called primitive plants may have several million cells. Plants have an alternation of generations where the sporophyte phase is succeeded by the gametophyte phase. The sporophyte phase produces spores within the sporangium by meiosis.
Flowering plants
Flowers are the sexual organs of flowering plants.

Flowering plants are the dominant plant form on land and they reproduce by sexual and asexual means. Often their most distinguishing feature is their reproductive organs, commonly called flowers. The anther produces male gametophytes, the sperm is produced in pollen grains, which attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located. After the pollen tube grows through the carpel's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization. The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female cells) and female tissues of the ovule give rise to the surrounding tissues in the developing seed. The ovary, which produced the female gametophyte(s), then grows into a fruit, which surrounds the seed(s). Plants may either self-pollinate or cross-pollinate. Nonflowering plants like ferns, moss and liverworts use other means of sexual reproduction.
Ferns

Ferns mostly produce large diploid sporophytes with rhizomes, roots and leaves; and on fertile leaves called sporangium, spores are produced. The spores are released and germinate to produce short, thin gametophytes that are typically heart shaped, small and green in color. The gametophytes or thallus, produce both motile sperm in the antheridia and egg cells in separate archegonia. After rains or when dew deposits a film of water, the motile sperm are splashed away from the antheridia, which are normally produced on the top side of the thallus, and swim in the film of water to the archegonia where they fertilize the egg. To promote out crossing or cross fertilization the sperm are released before the eggs are receptive of the sperm, making it more likely that the sperm will fertilize the eggs of different thallus. A zygote is formed after fertilization, which grows into a new sporophytic plant. The condition of having separate sporephyte and gametophyte plants is called alternation of generations. Other plants with similar reproductive means include the Psilotum, Lycopodium, Selaginella and Equisetum.
Bryophytes

The bryophytes, which include liverworts, hornworts and mosses, reproduce both sexually and vegetatively. They are small plants found growing in moist locations and like ferns, have motile sperm with flagella and need water to facilitate sexual reproduction. These plants start as a haploid spore that grows into the dominate form, which is a multicellular haploid body with leaf-like structures that photosynthesize. Haploid gametes are produced in antherida and archegonia by mitosis. The sperm released from the antherida respond to chemicals released by ripe archegonia and swim to them in a film of water and fertilize the egg cells thus producing a zygote. The zygote divides by mitotic division and grows into a sporophyte that is diploid. The multicellular diploid sporophyte produces structures called spore capsules, which are connected by seta to the archegonia. The spore capsules produce spores by meiosis, when ripe the capsules burst open and the spores are released. Bryophytes show considerable variation in their breeding structures and the above is a basic outline. Also in some species each plant is one sex while other species produce both sexes on the same plant.

Sex

In biology, sexual reproduction is a process of combining and mixing genetic traits, often resulting in the specialization of organisms into a male or female variety, each known as a sex.[1] Sexual reproduction involves combining specialized cells (gametes) to form offspring that inherit traits from both parents. Gametes can be identical in form and function (known as isogametes), but in many cases an asymmetry has evolved such that two sex-specific types of gametes (heterogametes) exist: male gametes are small, motile, and optimized to transport their genetic information over a distance, while female gametes are large, non-motile and contain the nutrients necessary for the early development of the young organism.

An organism's sex is defined by the gametes it produces: males produce male gametes (spermatozoa, or sperm) while females produce female gametes (ova, or egg cells); individual organisms which produce both male and female gametes are termed hermaphroditic. Frequently, physical differences are associated with the different sexes of an organism; these sexual dimorphisms can reflect the different reproductive pressures the sexes experience.
It is considered that sexual reproduction in eukaryotes first appeared about a billion years ago and evolved within ancestral single-celled eukaryotes.[2] The reason for the initial evolution of sex, and the reason(s) it has survived to the present, are still matters of debate. Some of the many plausible theories include: that sex creates variation among offspring, sex helps in the spread of advantageous traits, that sex helps in the removal of disadvantageous traits, and that sex evolved as an adaptation for repairing damages in DNA (see Evolution of sexual reproduction).

While there are a number of theories, there are two main alternative views on the evolutionary origin and adaptive significance of sex. The first view assumes that sexual reproduction is a process specific to eukaryotes, organisms whose cells contain a nucleus and mitochondria. In addition to sex in animals, plants, and fungi, there are other eukaryotes (e.g. the malaria parasite) that also engage in sexual reproduction. On this first view, the adaptive advantage that maintains sexual reproduction (in competition with asexual modes of reproduction) is the benefit of generating genetic variation among progeny. Furthermore, on this view, sex originated in a eukaryotic lineage. The earliest eukaryotes and the bacterial ancestors from which they arose are assumed to have lacked sex. For instance, some bacteria use conjugation to transfer genetic material between cells; and while not the same as sexual reproduction, this also results in the mixture of genetic traits. The reason that bacterial conjugation is not the same as sexual reproduction is that the numerous genes necessary for conjugation are not located on the bacterial chromosome, but on small circular DNA self-replicating parasitic elements called conjugative plasmids. Thus, conjugation arises from an adaptation of parasitic DNA for its own transmission.[3]

The second alternative view on the evolutionary origin and adaptive significance of sex is that sex existed in early bacteria as the process of natural transformation, a well studied DNA exchange process still in existence in many present day bacterial species (see Transformation (genetics)). Transformation involves the transfer of DNA from a donor to a recipient bacterium. Recipient bacteria must first enter a special physiological state, termed competence, to receive donor DNA (see Natural competence). The numerous genes necessary for establishment of competence are located on the bacterial chromosome itself. Thus the process of transformation is likely beneficial to bacteria, and can be regarded as a simple form of sex. In general, competence is induced under stressful conditions, such as nutrient limitation and exposure to DNA damaging agents, as reviewed by a number of authors.[4][5][6] Sex, on this view, was present in the earliest single-celled eukaryotes because they were descended from ancestral bacteria capable of transformation. Sex was maintained as an adaptation for repairing DNA damage (see Evolution of sexual reproduction). In particular, meiosis the key stage of the sexual cycle of eukaryotes, in which genetic information derived from different individuals (parents) recombines, was likely derived from the analogous, but simpler, genetic information exchange and DNA repair process that occurs during transformation in bacteria[7][8][9][10] (and also see Meiosis, section: Origin and function of meiosis). Thus, by this view, sex appears to have evolved in bacteria as a way of repairing DNA damages induced by environmental stresses, was maintained through the prokaryote/eukaryote boundary, and continued to evolve in higher multicellular eukaryotes, in part, as a DNA repair process.

What is considered defining of sexual reproduction in eukaryotes is the difference between the gametes and the binary nature of fertilization. Multiplicity of gamete types within a species would still be considered a form of sexual reproduction. However, no third gamete is known in multicellular animals.[11][12][13]

While the evolution of sex itself dates to the prokaryote or early eukaryote stage, the origin of chromosomal sex determination may have been fairly early in eukaryotes. The ZW sex-determination system is shared by birds, some fish and some crustaceans. Most mammals, but also some insects (Drosophila) and plants (Ginkgo) use XY sex-determination. X0 sex-determination is found in certain insects.

No genes are shared between the avian ZW and mammal XY chromosomes,[14] and from a comparison between chicken and human, the Z chromosome appeared similar to the autosomal chromosome 9 in human, rather than X or Y, suggesting that the ZW and XY sex-determination systems do not share an origin, but that the sex chromosomes are derived from autosomal chromosomes of the common ancestor of birds and mammals. A paper from 2004 compared the chicken Z chromosome with platypus X chromosomes and suggested that the two systems are related.
Sexual reproduction in eukaryotes is a process whereby organisms form offspring that combine genetic traits from both parents. Chromosomes are passed on from one generation to the next in this process. Each cell in the offspring has half the chromosomes of the mother and half of the father.[16] Genetic traits are contained within the deoxyribonucleic acid (DNA) of chromosomes – by combining one of each type of chromosomes from each parent, an organism is formed containing a doubled set of chromosomes. This double-chromosome stage is called "diploid", while the single-chromosome stage is "haploid". Diploid organisms can, in turn, form haploid cells (gametes) that randomly contain one of each of the chromosome pairs, via meiosis.[17] Meiosis also involves a stage of chromosomal crossover, in which regions of DNA are exchanged between matched types of chromosomes, to form a new pair of mixed chromosomes. Crossing over and fertilization (the recombining of single sets of chromosomes to make a new diploid) result in the new organism containing a different set of genetic traits from either parent.

In many organisms, the haploid stage has been reduced to just gametes specialized to recombine and form a new diploid organism; in others, the gametes are capable of undergoing cell division to produce multicellular haploid organisms. In either case, gametes may be externally similar, particularly in size (isogamy), or may have evolved an asymmetry such that the gametes are different in size and other aspects (anisogamy).[18] By convention, the larger gamete (called an ovum, or egg cell) is considered female, while the smaller gamete (called a spermatozoon, or sperm cell) is considered male. An individual that produces exclusively large gametes is female, and one that produces exclusively small gametes is male. An individual that produces both types of gametes is a hermaphrodite; in some cases hermaphrodites are able to self-fertilize and produce offspring on their own, without a second organism.[19]
Animals
Hoverflies engaging in sexual intercourse

Most sexually reproducing animals spend their lives as diploid organisms, with the haploid stage reduced to single cell gametes.[20] The gametes of animals have male and female forms—spermatozoa and egg cells. These gametes combine to form embryos which develop into a new organism.

The male gamete, a spermatozoon (produced within a testicle), is a small cell containing a single long flagellum which propels it.[21] Spermatozoa are extremely reduced cells, lacking many cellular components that would be necessary for embryonic development. They are specialized for motility, seeking out an egg cell and fusing with it in a process called fertilization.

Female gametes are egg cells (produced within ovaries), large immobile cells that contain the nutrients and cellular components necessary for a developing embryo.[22] Egg cells are often associated with other cells which support the development of the embryo, forming an egg. In mammals, the fertilized embryo instead develops within the female, receiving nutrition directly from its mother.

Animals are usually mobile and seek out a partner of the opposite sex for mating. Animals which live in the water can mate using external fertilization, where the eggs and sperm are released into and combine within the surrounding water.[23] Most animals that live outside of water, however, must transfer sperm from male to female to achieve internal fertilization.

In most birds, both excretion and reproduction is done through a single posterior opening, called the cloaca—male and female birds touch cloaca to transfer sperm, a process called "cloacal kissing".[24] In many other terrestrial animals, males use specialized sex organs to assist the transport of sperm—these male sex organs are called intromittent organs. In humans and other mammals this male organ is the penis, which enters the female reproductive tract (called the vagina) to achieve insemination—a process called sexual intercourse. The penis contains a tube through which semen (a fluid containing sperm) travels. In female mammals the vagina connects with the uterus, an organ which directly supports the development of a fertilized embryo within (a process called gestation).

Because of their motility, animal sexual behavior can involve coercive sex. Traumatic insemination, for example, is used by some insect species to inseminate females through a wound in the abdominal cavity – a process detrimental to the female's health.
Plants
Flowers are the sexual organs of flowering plants, usually containing both male and female parts.
Main article: Plant reproduction

Like animals, plants have developed specialized male and female gametes.[25] Within most familiar plants, male gametes are contained within hard coats, forming pollen. The female gametes of plants are contained within ovules; once fertilized by pollen these form seeds which, like eggs, contain the nutrients necessary for the development of the embryonic plant.
Pinus nigra cone.jpg     Pine cones, immature male.jpg
Female (left) and male (right) cones are the sex organs of pines and other conifers.

Many plants have flowers and these are the sexual organs of those plants. Flowers are usually hermaphroditic, producing both male and female gametes. The female parts, in the center of a flower, are the carpels—one or more of these may be merged to form a single pistil. Within carpels are ovules which develop into seeds after fertilization. The male parts of the flower are the stamens: these long filamentous organs are arranged between the pistil and the petals and produce pollen at their tips. When a pollen grain lands upon the top of a carpel, the tissues of the plant react to transport the grain down into the carpel to merge with an ovule, eventually forming seeds.

In pines and other conifers the sex organs are conifer cones and have male and female forms. The more familiar female cones are typically more durable, containing ovules within them. Male cones are smaller and produce pollen which is transported by wind to land in female cones. As with flowers, seeds form within the female cone after pollination.

Because plants are immobile, they depend upon passive methods for transporting pollen grains to other plants. Many plants, including conifers and grasses, produce lightweight pollen which is carried by wind to neighboring plants. Other plants have heavier, sticky pollen that is specialized for transportation by insects. The plants attract these insects with nectar-containing flowers. Insects transport the pollen as they move to other flowers, which also contain female reproductive organs, resulting in pollination.
Most fungi reproduce sexually, having both a haploid and diploid stage in their life cycles. These fungi are typically isogamous, lacking male and female specialization: haploid fungi grow into contact with each other and then fuse their cells. In some of these cases the fusion is asymmetric, and the cell which donates only a nucleus (and not accompanying cellular material) could arguably be considered "male".[26]

Some fungi, including baker's yeast, have mating types that create a duality similar to male and female roles. Yeast with the same mating type will not fuse with each other to form diploid cells, only with yeast carrying the other mating type.[27]

Fungi produce mushrooms as part of their sexual reproduction. Within the mushroom diploid cells are formed, later dividing into haploid spores—the height of the mushroom aids the dispersal of these sexually produced offspring.

Dance

Dance is a type of art that generally involves movement of the body, often rhythmic and to music. It is performed in many cultures as a form of emotional expression, social interaction, or exercise, in a spiritual or performance setting, and is sometimes used to express ideas or tell a story. Dance may also be regarded as a form of nonverbal communication between humans or other animals, as in bee dances and behaviour patterns such as a mating dances.

Definitions of what constitutes dance can depend on social and cultural norms and aesthetic, artistic and moral sensibilities. Definitions may range from functional movement (such as folk dance) to virtuoso techniques such as ballet. Martial arts kata are often compared to dances, and sports such as gymnastics, figure skating and synchronized swimming are generally thought to incorporate dance. In some cases, the motion of ordinarily inanimate objects may be described as dance (the leaves danced in the wind).

There are many styles and genres of dance. African dance is interpretative. Ballet, ballroom and tango are classical dance styles. Square dance and electric slide are forms of step dance, and breakdancing is a type of street dance. Dance can be participatory, social, or performed for an audience. It can also be ceremonial, competitive or erotic. Dance movements may be without significance in themselves, as in ballet or European folk dance, or have a gestural vocabulary or symbolic meaning as in some Asian dances.

Choreography is the art of creating dances. The person who creates (i.e., choreographs) a dance is known as the choreographer.
 Origins and history
Main article: History of dance
Ancient Greek bronze statuette of a veiled and masked dancer, 3rd - 2nd century BC, found in Alexandria, Egypt.

Dance does not leave behind clearly identifiable physical artifacts such as stone tools, hunting implements or cave paintings. It is not possible to say when dance became part of human culture.

Joseph Jordania recently suggested that dance, together with rhythmic music and body painting, was designed by the forces of natural selection at the early stage of hominid evolution as a potent tool to put groups of human ancestors in a battle trance, a specific altered state of consciousness. In this state hominids were losing their individual identity and were acquiring collective identity.[1] Jonathan Pieslak's research shows that some contemporary military units use loud group singing and dancing in order to prepare themselves for the dangerous combat missions.[2] According to Jordania, this trance-inducing ability of dance comes from human evolutionary past and includes as well a phenomenon of military drill[3] which is also based on shared rhythmic and monotonous group activity.

Dance has certainly been an important part of ceremony, rituals, celebrations and entertainment since before the birth of the earliest human civilizations. Archeology delivers traces of dance from prehistoric times such as the 9,000 year old Rock Shelters of Bhimbetka paintings in India and Egyptian tomb paintings depicting dancing figures from c. 3300 BC.

One of the earliest structured uses of dances may have been in the performance and in the telling of myths. It was also sometimes used to show feelings for one of the opposite gender. It is also linked to the origin of "love making." Before the production of written languages, dance was one of the methods of passing these stories down from generation to generation.[4]

Another early use of dance may have been as a precursor to ecstatic trance states in healing rituals. Dance is still used for this purpose by many cultures from the Brazilian rainforest to the Kalahari Desert.[5]

Sri Lankan dances goes back to the mythological times of aboriginal yingyang twins and "yakkas" (devils). According to a Sinhalese legend, Kandyan dances originated 250 years ago, from a magic ritual that broke the spell on a bewitched king. Many contemporary dance forms can be traced back to historical, traditional, ceremonial, and ethnic dance.
Classification and genres

Partner Dancing in Art
Dance at Bougival by Pierre-Auguste Renoir (1882–83)
Eadweard Muybridge's phenakistoscope "A Couple Waltzing" (c.1893)
Main articles: List of basic dance topics and List of dances

Dance categories by number of interacting dancers are mainly solo dance, partner dance and group dance. Dance is performed for various purposes like ceremonial dance, erotic dance, performance dance, social dance etc.
Dancing and music
Morris dancing in the grounds of Wells Cathedral, Wells, England
See also: Category:Music genres

Many early forms of music and dance were created and performed together. This paired development has continued through the ages with dance/music forms such as: jig, waltz, tango, disco, salsa, electronica and hip-hop. Some musical genres have a parallel dance form such as baroque music and baroque dance; others, such as classical music and classical ballet, developed separately.

Although dance is often accompanied by music, it can also be presented independently or provide its own accompaniment (tap dance). Dance presented with music may or may not be performed in time to the music depending on the style of dance. Dance performed without music is said to be danced to its own rhythm[citation needed].

Ballroom dancing is a dance art form which combines athletic fitness with artistically skillful dance steps.
Dance studies and techniques
See also: Dance theory, Choreography, and Dance moves

In the early 1920s, dance studies (dance practice, critical theory, Musical analysis and history) began to be considered as an academic discipline. Today these studies are an integral part of many universities' arts and humanities programs. By the late 20th century the recognition of practical knowledge as equal to academic knowledge led to the emergence of practice research and practice as research. A large range of dance courses are available including:

    Professional practice: performance and technical skills
    Practice research: choreography and performance
    Ethnochoreology, encompassing the dance-related aspects of: anthropology, cultural studies, gender studies, area studies, postcolonial theory, ethnography, etc.
    Dance therapy, or dance-movement therapy
    Dance and technology: new media and performance technologies
    Laban Movement Analysis and somatic studies

Academic degrees are available from BA (Hons) to PhD and other postdoctoral fellowships, with some dance scholars taking up their studies as mature students after a professional dance career.
Dance competitions
An amateur dancesport competition at MIT

A dance competition is an organized event in which contestants perform dances before a judge or judges for awards, and in some cases, monetary prizes. There are several major types of dance competitions, distinguished primarily by the style or styles of dances performed. Major types of dance competitions include:

    Competitive dance, in which a variety of theater dance styles such as: acro, ballet, jazz, hip-hop, lyrical, and tap, are permitted.
    Open competitions, that permit a wide variety of dance styles. A popular example of this is the TV program So You Think You Can Dance.
    Dancesport, which is focused exclusively on ballroom and latin dance. Popular examples of this are TV programs Dancing with the Stars and Strictly Come Dancing.
    Single-style competitions, such as; highland dance, dance team, and Irish dance, that only permit a single dance style.

Today, there are various dances and dance show competitions on television and the Internet.
Occupations
Main article: List of dance occupations
Saman dance from Gayo people of Sumatra, Indonesia

There are several careers connected with dancing: Dancer, dance teacher, dance sport coach, dance therapist and choreographer.

Dancer

Dance training differs depending on the dance form. There are university programs and schools associated with professional dance companies for specialised training in classical dance (e.g. Ballet) and modern dance. There are also smaller, privately owned dance studios where students may train in a variety of dance forms including competitive dance forms (e.g. Latin dance, ballroom dance, etc.) as well as ethnic/traditional dance forms.

Professional dancers are usually employed on contract or for particular performances/productions. The professional life of a dancer is generally one of constantly changing work situations, strong competition pressure and low pay. Professional dancers often need to supplement their income, either in dance related roles (e.g., dance teaching, dance sport coaches, yoga) or Pilates instruction to achieve financial stability.

In the U.S. many professional dancers are members of unions such as the American Guild of Musical Artists, the Screen Actors Guild and Actors' Equity Association. The unions help determine working conditions and minimum salaries for their members.
Professional dancers at the Tropicana Club, Havana, Cuba, in 2008

Dance teachers

Dance teacher and operators of dance schools rely on reputation and marketing. For dance forms without an association structure such as Salsa or Tango Argentino they may not have formal training. Most dance teachers are self-employed.

Dancesport coaches

Dancesport coaches are tournament dancers or former dancesports people, and may be recognised by a dance sport federation.

Choreographer

Choreographers are generally university trained and are typically employed for particular projects or, more rarely may work on contract as the resident choreographer for a specific dance company. A choreographic work is protected intellectual property. Dancers may undertake their own choreography.
By ethnicity or region
Main article: List of ethnic, regional, and folk dances sorted by origin
India
South indian folk dance like a horse known as Poi Kal Kudirai
Main article: Dance in India

During the first millennium BCE in India, many texts were composed which attempted to codify aspects of daily life. In the matter of dance, Bharata Muni's Natyashastra (literally "the text of dramaturgy") is one of the earlier texts. Though the main theme of Natyashastra deals with drama, dance is also widely featured, and indeed the two concepts have ever since been linked in Indian culture. The text elaborates various hand-gestures or mudras and classifies movements of the various limbs of the body, gait, and so on. The Natyashastra categorised dance into four groups and into four regional varieties, naming the groups: secular, ritual, abstract, and, interpretive. However, concepts of regional geography has altered and so have regional varieties of Indian dances. Dances like "Odra Magadhi", which after decades long debate, has been traced to present day Mithila, Odisha region's dance form of Odissi (Orissi), indicate influence of dances in cultural interactions between different regions.[6]

From these beginnings rose the various classical styles which are recognised today. Therefore, all Indian classical dances are to varying degrees rooted in the Natyashastra and therefore share common features: for example, the mudras, some body positions, and the inclusion of dramatic or expressive acting or abhinaya. The Indian classical music tradition provides the accompaniment for the dance, and as percussion is such an integral part of the tradition, the dancers of nearly all the styles wear bells around their ankles to counterpoint and complement the percussion.
Bhangra in the Punjab
Main article: Bhangra

The Punjab area overlapping India and Pakistan is the place of origin of Bhangra. It is widely known both as a style of music and a dance. It is mostly related to ancient harvest celebrations, love, patriotism or social issues. Its music is coordinated by a musical instrument called the 'Dhol'. Bhangra is not just music but a dance, a celebration of the harvest where people beat the dhol (drum), sing Boliyaan (lyrics) and dance.It developed further with the Vaisakhi festival of the Sikhs.
Dances of Sri Lanka
Main article: Dances of Sri Lanka

The devil dances of Sri Lanka or "yakun natima" are a carefully crafted ritual with a history reaching far back into Sri Lanka's pre-Buddhist past. It combines ancient "Ayurvedic" concepts of disease causation with psychological manipulation. The dance combines many aspects including Sinhalese cosmology, the dances also has an impact on the classical dances of Sri Lanka.[7]
Harlequin and Columbine from the mime theater at Tivoli Gardens, Copenhagen, Denmark
In Europe and North America
Concert (or performance) dance
Main article: Concert dance
Ballet
Main article: Ballet

Ballet developed first in Italy and then in France from lavish court spectacles that combined music, drama, poetry, song, costumes and dance. Members of the court nobility took part as performers. During the reign of Louis XIV, himself a dancer, dance became more codified. Professional dancers began to take the place of court amateurs, and ballet masters were licensed by the French government. The first ballet dance academy was the Académie Royale de Danse (Royal Dance Academy), opened in Paris in 1661. Shortly thereafter, the first institutionalized ballet troupe, associated with the Academy, was formed; this troupe began as an all-male ensemble but by 1681 opened to include women as well.[4]
A small dance company rehearses for an outdoor performance in Stuyvesant Cove Park in Manhattan, New York City
20th-century concert dance
Main article: 20th century concert dance

At the beginning of the 20th century, there was an explosion of innovation in dance style characterized by an exploration of freer technique. Early pioneers of what became known as modern dance include Loie Fuller, Isadora Duncan, Mary Wigman and Ruth St. Denis. The relationship of music to dance serves as the basis for Eurhythmics, devised by Emile Jaques-Dalcroze, which was influential to the development of Modern dance and modern ballet through artists such as Marie Rambert. Eurythmy, developed by Rudolf Steiner and Marie Steiner-von Sivers, combines formal elements reminiscent of traditional dance with the new freer style, and introduced a complex new vocabulary to dance. In the 1920s, important founders of the new style such as Martha Graham and Doris Humphrey began their work. Since this time, a wide variety of dance styles have been developed; see Modern dance.
The influence of African American dance
Main article: African American dance

African American dances are those dances which have developed within African American communities in everyday spaces, rather than in dance studios, schools or companies and its derivatives, tap dance, disco, jazz dance, swing dance, hip hop dance and breakdance. Other dances, such as the lindy hop with its relationship to rock and roll music and rock and roll dance have also had a global influence.

U.S. state

A state of the United States of America is one of the fifty constituent political entities that shares its sovereignty with the United States federal government. Because of the shared sovereignty between each U.S. state and the U.S. federal government, an American is a citizen of both the federal republic and of his or her state of domicile.[1] State citizenship and residency are flexible and no government approval is required to move between states, except for persons covered by certain types of court orders (e.g., paroled convicts and children of divorced spouses who are sharing custody).

States are divided into counties or county-equivalents, which may be assigned some local governmental authority but are not sovereign. County or county-equivalent structure varies widely by state. Kentucky, Massachusetts, Pennsylvania, and Virginia use the official title of Commonwealth rather than State.

The United States Constitution allocates certain powers to the federal government. It also places limitations on the federal and state governments. State governments are allocated power by the people (of each respective state) through their individual constitutions. By ratifying the United States Constitution, the states transferred certain limited sovereign powers to the federal government. Under the Tenth Amendment, all powers not delegated to the federal government nor prohibited to the states are retained by the states or the people.

Historically, the tasks of public safety (in the sense of controlling crime), public education, public health, transportation, and infrastructure have generally been considered primarily state responsibilities, although all of these now have significant federal funding and regulation as well (based largely upon the Commerce Clause, the Taxing and Spending Clause, and the Necessary and Proper Clause of the U.S. Constitution).

Over time, the U.S. Constitution has been amended, and the interpretation and application of its provisions have changed. The general tendency has been toward centralization and incorporation, with the federal government playing a much larger role than it once did. There is a continuing debate over states' rights, which concerns the extent and nature of the states' powers and sovereignty in relation to the federal government as well as the rights of individual persons. Debates over states' rights were a contributing factor to the outbreak of the American Civil War.

The United States Congress may admit new states on an equal footing with existing ones; this last happened in 1959 with the admission of Alaska and Hawaii. The U.S. Constitution is silent on the question of whether states have the power to leave unilaterally, or secede from, the Union, but the U.S. Supreme Court has ruled[2][3] secession to be unconstitutional, a position driven in part by the outcome of the American Civil War.

Main article: List of U.S. states

 Alabama
 Alaska
 Arizona
 Arkansas
 California
 Colorado
 Connecticut
 Delaware
 Florida
Georgia      Hawaii
 Idaho
 Illinois
 Indiana
 Iowa
 Kansas
 Kentucky
 Louisiana
 Maine
 Maryland      Massachusetts
 Michigan
 Minnesota
 Mississippi
 Missouri
 Montana
 Nebraska
 Nevada
 New Hampshire
 New Jersey      New Mexico
 New York
 North Carolina
 North Dakota
 Ohio
 Oklahoma
 Oregon
 Pennsylvania
 Rhode Island
 South Carolina      South Dakota
 Tennessee
 Texas
 Utah
 Vermont
 Virginia
 Washington
 West Virginia
 Wisconsin
 Wyoming

Federal power

The Supreme Court of the United States has interpreted the Commerce Clause of the Constitution of the United States which has expanded the scope of federal power. The Cambridge Economic History of the United States says, "On the whole, especially after the mid-1880s, the Court construed the Commerce Clause in favor of increased federal power."[4] In Wickard v. Filburn 317 U.S. 111 (1942), the court expanded federal power to regulate the economy by holding that federal authority under the commerce clause extends to activities which are local in character.[5] For example, Congress can regulate railway traffic across state lines, but it may also regulate rail traffic solely within a state, based on the theory that wholly intrastate traffic can still have an impact on interstate commerce. In recent years, the Court has tried to place limits on the Commerce Clause in such cases as United States v. Lopez and United States v. Morrison.[clarification needed]

Another source of congressional power is its spending power—the ability of Congress to impose taxes and distribute the resulting revenue back to the states (subject to conditions set by Congress). A classic example of this is the system of federal-aid highways, which includes the Interstate Highway System. The system is mandated and largely funded by the federal government, and also serves the interests of the states. By threatening to withhold federal highway funds, Congress has been able to pressure state legislatures to pass a variety of laws. Although some object that this infringes on states' rights, the Supreme Court upheld the practice as a permissible use of the Constitution's Spending Clause in South Dakota v. Dole 483 U.S. 203 (1987).
Governments

States are free to organize their individual governments any way they like, so long as they conform to the sole requirement of the U.S. Constitution that they have "a Republican Form of Government," that is, each state government must be a republic.
Constitutions

In practice, each state has adopted a three-branch system of government (with legislative, executive, and judiciary branches) generally along the same lines as that of the federal government — though this is not a requirement.

Despite the fact that every state has chosen to follow the federal model of government, there are significant differences in some states.

There are also significant similarities. For example, all 50 states allow tax exemptions for religious institutions.[6]
Executive

In all of the U.S. states, the chief executive is called the Governor. The governor may approve or veto bills passed by the state legislature. In forty-three states, governors have line item veto power.[7]

Most states have a "plural executive" in which two or more members of the executive branch are elected directly by the people. Such additional elected officials serve as members of the executive branch, but are not beholden to the governor and the governor cannot dismiss them. For example, the attorney general is elected, rather than appointed, in 43 of the 50 U.S. states.
Legislative
See also: State legislature (United States)

The legislatures of 49 of the 50 states are made up of two chambers: a lower house (termed the House of Representatives, State Assembly or House of Delegates) and a smaller upper house, always termed the Senate. The exception is the unicameral Nebraska Legislature, which is composed of only a single chamber.

Most states have part-time legislatures, while six of the most populated states have full-time legislatures. However, several states with high population have short legislative sessions, including Texas and Florida.[8]

In Baker v. Carr (1962) and Reynolds v. Sims (1964), the U.S. Supreme Court held that all states are required to elect their legislatures in such a way as to afford each citizen the same degree of representation (the one person, one vote standard). In practice, most states choose to elect legislators from single-member districts, each of which has approximately the same population. Some states, such as Maryland and Vermont, divide the state into single- and multi-member districts, in which case multi-member districts must have proportionately larger populations, e.g., a district electing two representatives must have approximately twice the population of a district electing just one.

If the governor vetoes legislation, all legislatures may override it, usually, but not always, requiring a two-thirds majority.
Judicial
See also: State court (United States) and state supreme court

States can also organize their judicial systems differently from the federal judiciary, as long as they protect the federal constitutional right of their citizens to procedural due process. Most have a trial level court, generally called a District Court or Superior Court, a first-level appellate court, generally called a Court of Appeal (or Appeals), and a Supreme Court. However, Oklahoma and Texas have separate highest courts for criminal appeals. New York state has its own terminology, in that the trial court is called the Supreme Court. Appeals are then taken to the Supreme Court, Appellate Division, and from there to the Court of Appeals.

Most states base their legal system on English common law (with substantial indigenous changes and incorporation of certain civil law innovations), with the notable exception of Louisiana, a former French colony, which draws large parts of its legal system from French civil law.

Only a few states choose to have the judges on the state's courts serve for life terms. In most of the states the judges, including the justices of the highest court in the state, are either elected or appointed for terms of a limited number of years, such as five years, eligible for re-election or reappointment if their performance is judged to be satisfactory.
Relationships
Among states

Under Article Four of the United States Constitution, which outlines the relationship between the states, the United States Congress has the power to admit new states to the Union. The states are required to give full faith and credit to the acts of each other's legislatures and courts, which is generally held to include the recognition of legal contracts, marriages, and criminal judgments, and before 1865, slavery status. States are prohibited from discriminating against citizens of other states with respect to their basic rights, under the Privileges and Immunities Clause. Under the Extradition Clause, a state must extradite people located there who have fled charges of "treason, felony, or other crimes" in another state if the other state so demands.
With the federal government

The states are guaranteed military and civil defense by the federal government, which is also required to ensure that the government of each state remains a republic.

Four states use the official name of Commonwealth, rather than State.[9] However, this is merely a paper distinction, and the U.S. Constitution uniformly refers to all of these subnational jurisdictions as "States" (Article One, Section 2, Clause 1 of the Constitution, concerning the U.S. House of Representatives, in which Representatives are to be elected by the people of the "States"; Article One, Section 3, Clause 1, concerning the U.S. Senate, allocates to each "State" two Senators). For all of these purposes, each of the four above-mentioned "Commonwealths" counts as a State.

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Anika Devi received her Bachelor’s degree in Media, Culture and Communication from New York University in 2012. She began freelancing for Business Solutions BD in 2010 and joined the team as a staff writer three years later. She currently serves as the assistant editor.
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