Sexual orientation is forms of attraction to people. There are many different groups. Some examples are: attraction to a different gender (heterosexuality), attraction to the same gender (homosexuality), attraction to more than one gender (bisexuality), and no attraction any gender (asexuality).

The groups are part of sexual identity. Some people use something such as pansexual or polysexual. Other people use nothing at all. Androphilia and gynephilia are an alternative to the gender binary in homosexual and heterosexual. Androphilia is attraction to a man or masculinity (any quality or behavior linked to a man). Gynephilia is attraction to a woman or femininity. Sexual preference overlaps with sexual orientation but is different. A bisexual person may like one gender more than another. Sexual preference may also give the idea of a degree of choice. The scientific consensus (position in the community of scientists) is that sexual orientation is not a choice.

Scientists do not know the exact cause of sexual orientation. It is thought that this is a complex combination of genetics, hormones, and environment. Scientists like any biological theory more than any social theory. This is because there is more proof that supports a biological cause of sexual orientation than a social one. There is little proof which gives the idea that early life experiences play a part in connection to sexual orientation.

Sexual orientation is important in biology, psychology, anthropology, history, and law.

Difference from sexual identity and sexual behavior

General 
Sexual orientation includes heterosexuality, bisexuality, and homosexuality, and asexuality. An asexual has little to no sexual attraction to people. This may be thought of as a lack of a sexual orientation. There is a large amount of discussion over whether or not this is a sexual orientation.

Most definitions of sexual orientation are one of two components. The focus is on the desire of an individual or the partner of the individual. Some people like to use the definition of the individual.

Sexual identity and sexual behavior are connected to sexual orientation but are different. Sexual identity is a concept of self. Sexual behavior is sex with other people. Sexual orientation is connections to other people. An individual may or may not show sexual orientation from behavior. A person who is not heterosexual by sexual orientation and has a heterosexual sexual identity is 'closeted'. This term may show a stage of change in any society that, little by little, attempts to support the sexual minority. In any sexual orientation study, scientists use the terms concordance (sexual attraction, sexual behavior, and sexual identity match) or discordance (sexual attraction, sexual behavior, and sexual identity do not match). Here is an example of discordance. A woman with attraction to women says she is heterosexual and only has sex with men. Sexual orientation (homosexual), sexual identity (heterosexual), and sexual behavior (heterosexual) of the woman do not match.

Sexual identity may also describe a perception of the sex of a person. Sexual preference is almost the same as sexual orientation. The main difference is sexual preference gives the idea of a degree of choice. The Committee on Sexual Orientation and Gender Diversity of the American Psychological Association says the term supports a "heterosexual bias".

Androphilia, gynephilia, and other terms 

Androphilia and gynephilia (or gynecophilia) are terms in behavioral science (the study of human and animal behavior) that describe sexual orientation. It is an alternative to the gender binary in homosexual and heterosexual. The terms describe the focus of attraction with no need to credit a sex assignment or gender identity to the person. Other terms such as pansexual and polysexual also do not make any connection to the person. People may also use terms such as queer, pansensual, polyfidelitous, or ambisexual.

Some scientists support use of the terms to skirt bias in concepts of human sexuality in the West. Sociologist Johanna Schmidt says that a term like "homosexual transsexual" cannot line up in a society where a third gender is supported. One example would be Samoan Fa’afafine.

Bruce Bagemihl is also against "homosexual transsexual". This is because Bageminl thought this makes it simple to say a straight transgender woman is a homosexual male looking to run from stigma.

Same gender loving (SGL) is a term by African Americans that is the same as homosexual.

Gender and social pressure 
Very early writers thought sexual orientation connects to the gender expression of the person. Karl Heinrich Ulrichs, Richard von Krafft-Ebing, Magnus Hirschfeld, Havelock Ellis, Carl Jung, and Sigmund Freud are some of the more famous writers. It was thought that a female person with attraction to female people is always masculine. Just the same, it was thought that a male person with attraction to male people is always feminine. This understanding of homosexuality as sexual inversion was a discussion at the time. By the second half of the 1900s, gender identity was seen as different from sexual orientation. Transgender and cisgender people may be attracted to men, women, or both. A homosexual, heterosexual, or bisexual person may be masculine, feminine, or androgynous. Still, studies by J. Michael Bailey and Kenneth Zucker say most of the gay men and lesbians describe different degrees of not matching gender roles as a child.

Today, the sexual orientation of transgender people match the gender. A trans woman who experiences attraction only to women is a lesbian. A trans man who experiences attraction only to women is a straight man.

Sexual orientation sees a more complex understanding of both sex (male, female, or intersex) and gender (man, woman, or third gender).

Outside of orientation 
A gay or lesbian person may do sexual behaviors with someone of a different gender for many reasons. One reason is the desire for a family that looks common. Another reason is to skirt bias. A third reason is to skirt punishment in religion and another reason is to simply be friends with benefits. Not all LGBT people keep quiet about orientation to a wife or husband. Some who come out as gay or lesbian have a healthy continuous heterosexual marriage.

Change 
Sexual identity can change through the life of an individual. This may or may not line up with sex, sexual behavior, or sexual orientation. Sexual orientation is stable and will not change for most people. Still, some tests say that some people may experience change in sexual orientation. This is more common for a woman than for a man.

Cause 
Scientists do not yet know the exact cause of sexual orientation. People thought that homosexuality was the result of wrong brain development. Early life experience and sexual abuse was thought to cause wrong brain development. This thought process comes from bias about homosexuality. Now many people guess that biology and environment play a complex part as a cause.

Biology 
Tests link many biological factors which may have relation to the development of sexual orientation. The factors are genes, prenatal hormones, and brain structure. Tests are continuous in this area.

Scientists have a belief that sexual orientation is not from any one factor. Instead, this is thought to be from a combination of genetics, hormones, and environment. There is more proof that supports a biological cause of sexual orientation than a social one. It is not thought that sexual orientation is a choice. Some scientists have the belief that this is set at fertilization. Statistics say there are biological differences between gay people and heterosexuals. This may result from the same cause as sexual orientation itself.

Genetic factors

Identical twins are more likely to have the same sexual orientation as fraternal twins. This means genes are linked to the development of sexual orientation. Studies have not found single 'gay genes', instead several thousand genes of a small influence are involved in sexual orientation. There are issues with the methods used in this research.

Hormones

The hormone theory of sexuality holds that certain hormones play a part in the sexual orientation that shows later in a mature person. Hormones in the fetus may be the prime effect on sexual orientation. This also may be one of many factors that combines with genes, environment, and social conditions to make a sexual orientation.

In humans, it is normal for females to have two X chromosomes. For males, it is normal to have one X chromosome and one Y chromosome. A human fetus starts as female so the Y chromosome is what makes the changes necessary to switch to male. Androgen hormones control this process. These androgens are testosterone and dihydrotestosterone (DHT). The testicles in the fetus are responsible for the existence of androgens. The androgens will work together to make the sex difference of the fetus. This results in differences between males and females. Some scientists change androgen levels in mammals during fetus and early life as experiments.

Birth Order

More than one study says the chance of homosexuality in a male increases with each successful birth of a male child. This effect ends if a male uses his left hand more than his right hand since birth.

Fraternal birth order (FBO) effect is a theory that has strong proof of its prenatal origin. No proof so far links this to an exact prenatal process. Tests give the idea that this may be from the immune system. This is a immune reaction from the mother against a substance important to the development of the male fetus. This reaction is even more probable after every successful male birth. It is thought that this immune effect changes future males prenatal development. This process is the maternal immunization hypothesis (MIH). This starts when cells from a male fetus enter the circulation of the mother. The immune system of the mother cannot support the Y proteins because she is female. This causes the development of antibodies. An antibody travels through the placenta into the section with the fetus. From here, an antibody crosses the blood–brain barrier of the brain of the fetus. This alters sex differences in brain structures relative to sexual orientation. This cause the son to experience more attraction to a man than a woman.

Social environment 
There is little proof to support the suggestion that early life experience or sexual abuse play a part in connection to sexual orientation. The viewpoints of parents may have an effect on how a child experiments with behaviors that link to a certain sexual orientation.

Effort to change sexual orientation 

A sexual orientation change effort is a plan that will try to change a same gender sexual orientation. This is cognitive behavioral therapy or conversion therapy.

No mental health organization gives approval to any effort to change sexual orientation. Almost all have a statement that says not to get a treatment that claims to change sexual orientation. Some orginizations with that statement are the American Psychiatric Association, American Psychological Association, American Counseling Association, National Association of Social Workers, Royal College of Psychiatrists, and Australian Psychological Society.

In 2012, the Pan American Health Organization makes a statement that says not to get a service that claims to change people with a not heterosexual sexual orientation. This is because there is no medical need. This is also a serious threat to the well-being of people that use this service. The scientific consensus of the world is that homosexuality is a normal and natural form of human sexuality. Homosexuality cannot be thought of as a disease. The Pan American Health Organization also says governments, schools, organizations, and communication outlets need to support respect for differences. Sometimes, a gay child will have to go to a "treatment" without choice. A gay child is sometimes put in a place separate from everyone for many months. Any places that have such poor treatment be subject to punishment under government law. This is for two reasons. The first reason is because this is against the moral concepts of medical care. The second reason is because this is against human rights that the international agreement keeps safe.

The National Association for Research & Therapy of Homosexuality (NARTH) takes takes issue with how the mental health society describes the success of conversion therapy. NARTH also takes issue with how the mental health society describes sexual orientation for two reasons. One reason is because it is not a fixed two part quality. The second reason is because it is not a disease. Instead, it describes as a continuous order of sexual attraction and emotional attraction. The American Psychological Association and the Royal College of Psychiatrists say there is trouble with the positions of the NARTH. Science cannot support the positions. The positions also make an environment in which bias increases.

Measure 
Different definitions and strong social rules about sexuality makes sexual orientation hard to measure.

Early organization systems 
In the 1860s, Karl Henrich Ulrichs makes small books about a sexual orientation organization system. The organization system is only for males. It separates males into three simple groups. The groups are dionings, urnings and uranodionings. Ulrichs outlines a set of questions to check if a man was an urning.

A dioning is the same as heterosexual male. An urning is the same as a homosexual male. An uranodioning is the same as a bisexual male.

Urnings are put into four groups.

A mannling is a masculine urning. A weibling is an effeminate urning. A zwischen is an androgynous urning. A virilised is an urning that will only have heterosex sex.

In 1896, Berlin sexologist Magnus Hirschfeld makes a system that measures the strength of sexual desire of an individual. This system measures on two different scales of 10 points. The scales are A (homosexual) and B (heterosexual). A heterosexual individual may be A0, B5. A homosexual individual may be A5, B0. An asexual is A0, B0. Someone with a strong attraction to both genders may be A9, B9.

Kinsey scale 
Alfred Kinsey, Wardell Pomeroy, and Clyde Martin made the Kinsey scale. This scale was in Sexual Behavior in the Human Male and Sexual Behavior in the Human Female. It was made to fight the idea that people can only be homosexual or heterosexual. Kinsey sees that much of population is not all heterosexual or all homosexual. Such people experience both heterosexual and homosexual behavior.

The Kinsey scale is an organization of sexual orientation. The position on the scale is based on the relation of heterosexuality to homosexuality in their history.

Even with eight groups, it is still hard determining which group will be good to put an individual in. Masters and Johnson talk about the difficulty of sexual comparisons with the Kinsey results. They find it hard to put an individual between the numbers 2 to 4 if the individual has a large amount of heterosexual and homosexual experiences. This is because it becomes hard for that individual to judge the relative amount of each without bias.

Kinsey thought about two areas of sexual orientation. The two areas are sexual reactions and sexual experiences. Weinrich says important information is lost when the two values combine into one final result. A person only with same gender sexual reactions is different from someone with little sexual reactions but a large amount of same gender sexual experiences. Also, there are more than two areas of sexuality to be thought about. Attraction and identity are other areas to judge. This is fixed in the Klein Sexual Orientation Grid.

A 1970s study on masculinity and femininity says that the concepts are better on separate scales. The scales are in place of single continuous scale. Each end of the scale is representative of total opposites. When on the same scale, one will have to decrease for the other to increase. To be more feminine, one has to be less masculine. To be more masculine, one has to be less feminine. However, if they are thought of as separate areas, one can be both very masculine and very feminine. In the same way, heterosexuality and homosexuality on separate scales would allow one to be both very heterosexual and very homosexual. Or someone can be not very much of either. This makes determining the degree of heterosexual and homosexual in an individual easy. It is easy because each area is thought as independent rather than attempts to match a specific balance like the Kinsey scale.

The Self Assessment of Sexual Orientation 
The Sell Assessment of Sexual Orientation (SASO) is an improvement on the Kinsey Scale and Klein Sexual Orientation Grid. SASO improves in three areas. It contains many sections of sexual orientation. It also separates homosexuality and heterosexuality. SASO can start discussions on the best ways to measure sexual orientation.

Discrimination 
Many people have been discriminated against because of their sexual orientation.  In many cultures, people who are homosexual or bisexual have been teased (made fun of), fired from their job, or made to suffer violence because of who they are.  In many countries and states, there are laws against having sex with somebody of the same gender, and people can be put in jail because of who they have sex with. In the United States, these laws were struck down (repealed) by the United States Supreme Court in the last few years. The Yogyakarta Principles are made to combat such discrimination and United Nations High Commissioner for Human Rights also made a document "Born Free and Equal" to counter them by international human rights law.

Related pages
Homophobia
Yogyakarta Principles
Romantic orientation

Note 

LGBT