Caprice is a sudden, unpredictable change of mind or behavior that seems to have no good reason behind it. When your friend agrees to play soccer at recess but then suddenly refuses because they “just don't feel like it anymore,” that's caprice. When a teacher announces a pop quiz on a whim, or when someone changes their lunch order three times for no clear reason, they're acting on caprice.

The word suggests more than simple indecision. Caprice has a quality of randomness or whimsy to it, like following wherever a fleeting mood leads. A person prone to caprice might be enthusiastic about learning piano one week, then abandon it the next for no clear reason. A ruler who governs by caprice makes decisions based on momentary impulses rather than consistent principles, which can make life unpredictable and difficult for everyone else.

Something capricious changes unpredictably. Weather can be capricious when it shifts from sunny to stormy without warning. A capricious person is hard to predict or rely on because their decisions seem to blow like the wind, changing direction for reasons only they understand, if there are reasons at all.