In modern English, gay has come to be used as an adjective, and as a noun, referring to the community, practices and cultures associated with homosexuality.
While scant usage referring to male homosexuality dates to the late 19th century, that meaning became increasingly common by the mid-20th century. The term originally meant 'carefree', 'cheerful', or 'bright and showy'.
Gay is a term that primarily refers to a homosexual person or the trait of being homosexual.
