1. the capacity to perceive or express the amusing aspects of a situation. There is little agreement about the essence of humor and the reasons one laughs or smiles at jokes or anecdotes. Among philosophers, both Plato (c. 427–c. 347 bce) and Thomas Hobbes claimed that individuals laugh at people and situations that make them feel superior, whereas Immanuel Kant emphasized surprise and anticlimax: “the sudden transformation of a strained expectation to nothing.” U.S. writer Max Eastman (1883–1969) saw humor as “playful pain,” a way of taking serious things lightly and thereby triumphing over them. Sigmund Freud called attention to the many jokes (especially those having to do with sex and hostility) that enable individuals to give free expression to forbidden impulses and explained laughter in terms of a release of the energy normally employed in keeping them out of consciousness. See also incongruity theory of humor; release theory of humor.

2. the semifluid substance that occupies the spaces in the eyeball. See aqueous humor; vitreous humor.

3. in antiquity, one of four bodily fluids (blood, black bile, yellow bile, and phlegm) that were thought to be responsible for a person’s physical and psychological characteristics (see humoral theory). This belief accounts for the use of the word humor to mean mood, as in good humor, or whim, as in It is her humor. —humoral adj. —humorous adj.