A malapropism is the mistaken use of a word in place of a similar-sounding one, producing a nonsensical or unintentionally comic effect. The error usually involves a showy or formal word.

The term comes from Mrs. Malaprop in Sheridan’s play The Rivals, who says “as headstrong as an allegory on the banks of the Nile” when she means “alligator.” Characters who aspire to elevated speech but lack the vocabulary often fall into malapropisms. The device is a staple of comic writing and of characterization through linguistic pretension.

Real-life malapropisms occur frequently in speech and sometimes in print. They differ from mere mispronunciation by substituting an actual, incorrect word. Writers use them to expose a character’s ignorance or vanity while amusing the audience, who recognize the intended word and enjoy the gap.

When a speaker reaches for a fancy word and seizes the wrong one, the result is a malapropism.