structural:reformatting
Etymology

The word homosexual is a Greek and Latin hybrid, with the first element derived from Greek ὁμός homos, "same" (not related to the Latin homo, "man", as in Homo sapiens), thus connoting sexual acts and affections between members of the same sex, including lesbianism. The first known appearance of homosexual in print is found in an 1868 letter to Karl Heinrich Ulrichs by the Austrian-born novelist Karl-Maria Kertbeny. arguing against a Prussian anti- sodomy law. In 1886, the psychiatrist Richard von Krafft-Ebing used the terms homosexual and heterosexual in his book Psychopathia Sexualis. Krafft-Ebing's book was so popular among both laymen and doctors that the terms heterosexual and homosexual became the most widely accepted terms for sexual orientation. As such, the current use of the term has its roots in the broader 19th-century tradition of personality taxonomy.

Many modern style guides in the U.S. recommend against using homosexual as a noun, instead using gay man or lesbian. Similarly, some recommend completely avoiding usage of homosexual as it has a negative, clinical history and because the word only refers to one's sexual behavior (as opposed to romantic feelings) and thus it has a negative connotation. Gay and lesbian are the most common alternatives. The first letters are frequently combined to create the initialism LGBT (sometimes written as GLBT), in which B and T refer to bisexual and transgender people.

Gay especially refers to male homosexuality, but may be used in a broader sense to refer to all LGBT people. In the context of sexuality, lesbian refers only to female homosexuality. The word lesbian is derived from the name of the Greek island Lesbos, where the poet Sappho wrote largely about her emotional relationships with young women.

Although early writers also used the adjective homosexual to refer to any single-sex context (such as an all-girls school), today the term is used exclusively in reference to sexual attraction, activity, and orientation. The term homosocial is now used to describe single-sex contexts that are not specifically sexual. There is also a word referring to same-sex love, homophilia.

Some synonyms for same-sex attraction or sexual activity include men who have sex with men or MSM (used in the medical community when specifically discussing sexual activity) and homoerotic (referring to works of art). Pejorative terms in English include queer, faggot, fairy, poof, poofter and homo. Beginning in the 1990s, some of these have been reclaimed as positive words by gay men and lesbians, as in the usage of queer studies, queer theory, and even the popular American television program Queer Eye for the Straight Guy. The word homo occurs in many other languages without the pejorative connotations it has in English. As with ethnic slurs and racial slurs, the use of these terms can still be highly offensive. The range of acceptable use for these terms depends on the context and speaker. Conversely, gay, a word originally embraced by homosexual men and women as a positive, affirmative term (as in gay liberation and gay rights), came into widespread pejorative use among young people in the early 2000s.

The American LGBT rights organization GLAAD advises the media to avoid using the term homosexual to describe gay people or same-sex relationships as the term is "frequently used by anti-gay extremists to denigrate gay people, couples and relationships".