These relationships are equivalent to heterosexual relationships in essential psychological respects. Many gay and lesbian people are in committed same-sex relationships. Homosexual behavior has also been documented in many non-human animal species, though homosexual orientation is not significantly observed in other animals. The percentage of people who are gay or lesbian and the proportion of people who are in same-sex romantic relationships or have had same-sex sexual experiences are difficult for researchers to estimate reliably for a variety of reasons, including many gay and lesbian people not openly identifying as such due to prejudice or discrimination such as homophobia and heterosexism. The most common adjectives for homosexual people are lesbian for females and gay for males, but the term gay also commonly refers to both homosexual females and males. There is insufficient evidence to support the use of psychological interventions to change sexual orientation.
While some people believe that homosexual activity is unnatural, scientific research shows that homosexuality is a normal and natural variation in human sexuality and is not in and of itself a source of negative psychological effects. There is no substantive evidence which suggests parenting or early childhood experiences play a role with regard to sexual orientation. There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males. Although no single theory on the cause of sexual orientation has yet gained widespread support, scientists favor biologically based theories. Scientists do not yet know the exact cause of sexual orientation, but they theorize that it is caused by a complex interplay of genetic, hormonal, and environmental influences and do not view it as a choice. It "also refers to a person's sense of identity based on those attractions, related behaviors, and membership in a community of others who share those attractions." Īlong with bisexuality and heterosexuality, homosexuality is one of the three main categories of sexual orientation within the heterosexual–homosexual continuum. As a sexual orientation, homosexuality is "an enduring pattern of emotional, romantic, and/or sexual attractions" to people of the same sex. Homosexuality is romantic attraction, sexual attraction, or sexual behavior between members of the same sex or gender.