A joke is a display of humour in which words are used within a specific and well-defined narrative structure to make people laugh and is usually not meant to be interpreted literally. It usually takes the form of a story, often with dialogue, and ends in a punch line, whereby the humorous element of the story is revealed; this can be done using a pun or other type of word play, irony or sarcasm, logical incompatibility, hyperbole, or other means. Linguist Robert Hetzron offers the definition:

A joke is a short humorous piece of oral literature in which the funniness culminates in the final sentence, called the punchline… In fact, the main condition is that the tension should reach its highest level at the very end. No continuation relieving the tension should be added. As for its being "oral," it is true that jokes may appear printed, but when further transferred, there is no obligation to reproduce the text verbatim, as in the case of poetry.

It is generally held that jokes benefit from brevity, containing no more detail than is needed to set the scene for the punchline at the end. In the case of riddle jokes or one-liners, the setting is implicitly understood, leaving only the dialogue and punchline to be verbalised. However, subverting these and other common guidelines can also be a source of humour—the shaggy dog story is an example of an anti-joke; although presented as a joke, it contains a long drawn-out narrative of time, place and character, rambles through many pointless inclusions and finally fails to deliver a punchline. Jokes are a form of humour, but not all humour is in the form of a joke. Some humorous forms which are not verbal jokes are: involuntary humour, situational humour, practical jokes, slapstick and anecdotes.

Identified as one of the simple forms of oral literature by the Dutch linguist André Jolles, jokes are passed along anonymously. They are told in both private and public settings; a single person tells a joke to his friend in the natural flow of conversation, or a set of jokes is told to a group as part of scripted entertainment. Jokes are also passed along in written form or, more recently, through the internet.

Stand-up comics, comedians and slapstick work with comic timing and rhythm in their performance, and may rely on actions as well as on the verbal punchline to evoke laughter. This distinction has been formulated in the popular saying "A comic says funny things; a comedian says things funny".