In Zen Buddhism, a brief paradoxical statement or question used as a discipline in meditation .
The effort to solve a koan is designed to exhaust the analytic intellect and the will, leaving the mind open for response on an intuitive level. There are about 1,700 traditional koans, which are based on anecdotes from ancient Zen masters. They include the well-known example "When both hands are clapped a sound is produced; listen to the sound of one hand clapping."