Stupidity is a lack of intelligence, understanding, reason, or wit. It may be innate, assumed or reactive. The word stupid comes from the Latin word stupere. Stupid characters are often used for comedy in fictional stories. Walter B. Pitkin called stupidity "evil", but in a more Romantic spirit William Blake and Carl Jung believed stupidity can be the mother of wisdom.

The root word stupid,[1] which can serve as an adjective or noun, comes from the Latin verb stupere, for being numb or astonished, and is related to stupor.[2] In Roman culture, the stupidus was the professional fall guy in the theatrical mimes.[3]

According to the online Merriam-Webster dictionary, the words "stupid" and "stupidity" entered the English language in 1541. Since then, stupidity has taken place along with "fool," "idiot," "dumb," "moron," and related concepts as a pejorative for misdeeds, whether purposeful or accidental, due to absence of mental capacity.