Gay is a term that primarily refers to a homosexual person or the trait of being homosexual. The term originally meant 'carefree', 'cheerful', or 'bright and showy'.

While scant usage referring to male homosexuality dates to the late 19th century, that meaning became increasingly common by the mid-20th century. 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. In the 1960s, gay became the word favored by homosexual men to describe their sexual orientation. By the end of the 20th century and beginning of the 21st century, the word gay was recommended by major LGBT groups and style guides to describe people attracted to members of the same sex, although it is more commonly used to refer specifically to men.

At about the same time, a new, pejorative use became prevalent in some parts of the world. Among younger speakers, the word has a meaning ranging from derision (e.g., equivalent to 'rubbish' or 'stupid') to a light-hearted mockery or ridicule (e.g., equivalent to 'weak', 'unmanly', or 'lame'). The extent to which these usages still retain connotations of homosexuality has been debated and harshly criticized.