Homosexuality is romantic attraction, sexual attraction, or sexual behavior between members of the same sex or gender.As a sexual orientation, homosexuality is "an enduring pattern of emotional, romantic, and/or sexual attractions" to people of the same sex. 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."

Along with bisexuality and heterosexuality, homosexuality is one of the three main categories of sexual orientation within the heterosexual–homosexual continuum. 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. Although no single theory on the cause of sexual orientation has yet gained widespread support, scientists favour biologically based theories. There is considerably more evidence supporting non-social, biological causes of sexual orientation than social ones, especially for males. There is no substantive evidence which suggests parenting or early childhood experiences play a role with regard to 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 insufficient evidence to support the use of psychological interventions to change sexual orientation.

The most common adjectives for homosexuals are lesbians for women and gays for men, but the term gay also generally refers to homosexual women and men. The percentage of people who are gay or lesbian, and the percentage of people who are in same-sex relationships or have had same-sex sexual experiences, are reliably estimated by researchers for a variety of reasons, including many gays and lesbians. is difficult to do. Do not confuse because of prejudice or openly identify discrimination such as homophobia or heterosexuality. Homosexual behaviour has also been documented in many non-human animal species, but humans are one of only two species known to exhibit homosexual orientation. same-sex relationship. These relationships are equivalent to heterosexual relationships in essential psychological aspects.