Fuck is an English-language profanity which often refers to the act of sexual intercourse, but is also commonly used as an intensifier or to convey disdain. While its origin is obscure, it is usually considered to be first attested to around 1475. In modern usage, the term fuck and its derivatives are used as a noun, a verb, an adjective, an interjection or an adverb. There are many common phrases that employ the word as well as compounds that incorporate it, such as motherfucker, fuckwit, fuckwad, fuckup, fucknut, fuckhead, fuckface, fucktard, and fuck off.

Profanity involves the use of notionally offensive words for a variety of purposes, including to demonstrate disrespect or negativity, to relieve pain, to express a strong emotion, as a grammatical intensifier or emphasis, or to express informality or conversational intimacy. In many formal or polite social situations, it is considered impolite, and in some religious groups it is considered a sin. Profanity includes slurs, but there are many insults that do not use swear words.