Eat a live toad in the morning, and nothing worse will happen to either of you for the rest of the day.

Almost everyone considers a sense of humor to be a prized human characteristic, but ask someone to define it and you'll typically get a muddled rather than precise definition. For example, try to explain why most folks think that the joke above is funny.

A sense of humor thus joins such commonly used fuzzy concepts as chair, vegetable, love, and fairness that lack the definitional precision of such concepts as female, even number, boat, and smile.