Homosexuality is romantic attraction, sexual attraction, or sexual behavior between people of the same sex or gender. It also denotes identity based on attraction, related behavior, and community affiliation.
Along with bisexuality and heterosexuality, homosexuality is one of the three main categories of sexual orientation within the heterosexual–homosexual continuum. Although no single theory on the cause of sexual orientation has yet gained widespread support, scientists favor biological theories. There is considerably more evidence supporting nonsocial, biological causes of sexual orientation than social ones, especially for males. A major hypothesis implicates the prenatal environment, specifically the organizational effects of hormones on the fetal brain. There is no substantive evidence which suggests parenting or early childhood experiences play a role in developing a sexual orientation. Scientific research shows that homosexuality is a natural and normal variation in human sexuality and is not in and of itself a source of negative psychological effects. Major mental health organizations overwhelmingly reject conversion therapy as ineffective, scientifically unsupported and potentially harmful.