A branch of Mahayana Buddhism which was brought to China (where it was called Chan) in 520 CE by Bodhidarma and arrived in Japan in the twelfth century. It is probably the most common form of Buddhism in the West. Practitioners of Zen must usually devote themselves to a life as a monk, for it requires extensive periods of meditation. It concentrates on making clear that reality is beyond words and language and beyond logic. To accomplish this, it makes use of the koan, zazen, and sanzen. The word "zen" derives from the Sanskrit term for the concept of jhana.