Humour or humor (see American and British English spelling differences) is the tendency of particular cognitive experiences to provoke laughter and provide amusement. Many theories exist about what humour is and what social function it serves. People of all ages and cultures respond to humour. The majority of people are able to be amused, to laugh or smile at something funny, and thus they are considered to have a "sense of humour."

The term derives from the humoral medicine of the ancient Greeks, which stated that a mix of fluids known as humours (Greek: χυμός, chymos, literally juice or sap; metaphorically, flavour) controlled human health and emotion. (This theory has since been found to be counterfactual.)[citation needed]

A sense of humour is the ability to experience humour, although the extent to which an individual will find something humorous depends on a host of variables, including geographical location, culture, maturity, level of education, intelligence, and context. For example, young children may possibly favour slapstick, such as Punch and Judy puppet shows or cartoons (e.g., Tom and Jerry). Satire may rely more on understanding the target of the humour, and thus tends to appeal to more mature audiences. Nonsatirical humour can be specifically termed "recreational drollery."