Homosexuality

Homosexuality refers to romantic or sexual attraction, or sexual behavior, between people of the same sex or gender. It can also describe a personal identity shaped by that attraction, related actions, or membership in a community. Alongside bisexuality and heterosexuality, it is one of the three primary categories of sexual orientation on the heterosexual–homosexual spectrum.

Causes

No single explanation for the cause of sexual orientation has broad scientific agreement, but researchers tend to favor biological theories. Evidence for nonsocial, biological origins—especially for males—is considerably stronger than evidence for social ones. A leading hypothesis points to the prenatal environment, particularly how hormones organize the developing fetal brain.

Psychology

There is no solid proof that parenting or early childhood experiences significantly influence sexual orientation. Scientific research indicates that homosexuality is a natural and normal variation in human sexuality and does not inherently cause negative psychological effects. Major mental health organizations overwhelmingly reject conversion therapy as ineffective, unsupported by science, and potentially harmful.

Homosexual behavior in other animals

Common terms for homosexual people are lesbian for women and gay for men, though gay often refers to both men and women. Reliably estimating how many people are gay or lesbian is difficult because many do not openly identify as such due to discrimination or prejudice like heterosexism or homophobia. Homosexual behavior appears in many non-human animal species, but domestic sheep are the only conclusively documented example of animals showing exclusive same-sex orientation.

Relationships

Many gay and lesbian individuals are in committed same-sex relationships, which are psychologically equivalent to heterosexual relationships in essential ways. Throughout history, homosexual relationships and acts have been both admired and condemned, depending on the culture and form they took. Since the late 20th century, a global movement has pushed for freedom and equality for gay people, including anti-bullying laws for teenagers, non-discrimination protections, equal military service, equal healthcare access, equal adoption and parenting rights, and marriage equality.

The word homosexual blends Greek homos ('same') with Latin roots, first appearing in an 1868 letter by Karl-Maria Kertbeny arguing against a Prussian anti-sodomy law. In 1886, psychiatrist Richard von Krafft-Ebing used homosexual and heterosexual in his book Psychopathia Sexualis, which popularized the terms. Many modern U.S. style guides advise against using homosexual as a noun, preferring gay man or lesbian. Some recommend avoiding homosexual entirely due to its clinical, negative history and its focus on sexual behavior rather than romantic feelings.

Gay and lesbian are the most common alternatives, often combined into the initialism LGBT (or GLBT), with B and T standing for bisexual and transgender people. Gay especially refers to male homosexuality but can broadly include all LGBTQ people. Lesbian specifically refers to female homosexuality, derived from the Greek island Lesbos, where poet Sappho wrote about emotional relationships with young women. Early writers used homosexual for any single-sex context, but today it mainly refers to sexual attraction, activity, and orientation; homosocial now describes nonsexual single-sex settings.

Homophilia is a synonym for same-sex love. Other terms include men who have sex with men (MSM, used medically) and homoerotic (for art). Pejorative English terms include queer, faggot, fairy, poof, poofter, and homo.

Since the 1990s, some of these—like queer—have been reclaimed positively, as in queer studies or Queer Eye for the Straight Guy. The word homo lacks pejorative connotations in many other languages. As with ethnic slurs, acceptable use depends on context and speaker. Conversely, gay, once embraced as a positive term in movements like gay liberation, became widely used pejoratively among young people in the early 2000s.

Same-sex relations appear throughout history, with acceptance varying by time and place. However, many historians and anthropologists caution against using terms like "homosexuality" for these practices, as it may create false equivalencies.