in Zen Buddhism of Japan, a succinct paradoxical statement or question used as a meditation discipline for novices, particularly in the Rinzai sect. The effort to “solve” a koan is intended to exhaust the analytic intellect and the egoistic will, readying the mind to entertain an appropriate response on the intuitive level. Each such exercise constitutes both a communication of some aspect of Zen experience and a test of the novice's competence.

A characteristic example of the style is the well-known koan “When both hands are clapped a sound is produced; listen to the sound of one hand clapping.” Sometimes the koan is set in question-and-answer form, as in the question “What is Buddha?” and its answer, “Three pounds of flax.”

Koans (from Chinese kung-an, literally “public notice,” or “public announcement”) are based on anecdotes of Zen (Chinese: Ch'an) masters. There are said to be 1,700 koans in all. The two major collections are the Pi-yen lu (Chinese: “Blue Cliff Records”; Japanese: Hekigan-roku), consisting of 100 koans selected and commented on by a Chinese priest, Yüan-wu, in 1125 on the basis of an earlier compilation; and the Wu-men kuan (Japanese: Mumon-kan), a collection of 48 koans compiled in 1228 by the Chinese priest Hui-k'ai (known also as Wu-men). Compare zazen. (zazen)