Zen, Chinese CH'AN (from Sanskrit dhyana, "meditation"), important school of Buddhism in Japan that claims to transmit the spirit or essence of Buddhism, which consists in experiencing the enlightenment (bodhi) achieved by Gautama the Buddha. The school arose in the 6th century in China as Ch'an, a form of Mahayana Buddhism; though introduced centuries earlier, Zen did not fully develop in Japan until the 12th century. In its secondary developments of mental tranquillity, fearlessness, and spontaneity--all faculties of the enlightened mind--the school of Zen has had lasting influence on the cultural life of Japan.

Zen teaches that the Buddha-nature, or potential to achieve enlightenment, is inherent in everyone but lies dormant because of ignorance. It is best awakened not by the study of scriptures, the practice of good deeds, rites and ceremonies, or worship of images but by a sudden breaking through of the boundaries of common, everyday, logical thought.

Training in the methods leading to such an enlightenment (Chinese wu; Japanese Satori,) is best transmitted personally from master to disciple. The methods recommended, however, differ among the various sects of Zen.

The Rinzai (Chinese: Lin-chi) sect, introduced to Japan from China by the priest Ensai in 1191, emphasizes sudden shock and meditation on the paradoxical statements called koan.

The Soto (Chinese: Ts'ao-tung) sect, transmitted to Japan by Dogen on his return from China in 1227, prefers the method of sitting in meditation (zazen).

A third sect, the Obaku (Chinese: Huang-po), was established in 1654 by the Chinese monk Yin-yüan (Japanese: Ingen). It employs the methods of Rinzai and also practices nembutsu, the continual invocation of Amida (the Japanese name for the Buddha Amitabha), with the devotional formula namu Amida Butsu (Japanese: "homage to Amida Buddha").

During the 16th-century period of political unrest, Zen priests not only contributed their talents as diplomats and administrators but also preserved the cultural life; it was under their inspiration that art, literature, the tea cult, and the no theatre, for example, developed and prospered. Neo-Confucianism, which became the guiding principle of the Tokugawa feudal regime (1603-1867), also was originally introduced and propagated by Japanese Zen masters.

In modern Japan, Zen sects and subsects claim some 9,600,000 adherents. Considerable interest in various aspects of Zen thought has developed also in Western countries in the latter half of the 20th century, and a number of Zen groups have been formed in North America and Europe.