Overview

The word zen is an abbreviation of the word zenna (also zenno), the Japanese way of reading Chinese ch'an-na (short form, ch'an).  This is turn is the Chinese version of the Sanskrit word dhyana, which refers to collectedness of mind or meditative absorption in which all dualistic distinctions like I/you, subject/object, and true/false are eliminated.  Zen can be defined both exoterically and esoterically.

Exoterically regarded, Zen , of Ch'an as it is called when referring to its history in China, is a school of Mahayana Buddhism that developed in China in the 6th and 7th centuries from the meeting of Dhyana Buddhism, which was brought to China by Bodhidharma, and Taoism.  In this sense Zen is a religion, the teachings and practices of which are directed toward self-realization and lead finally to complete awakening or enlightenment as experienced by Shakyamuni Buddha after intensive meditative self-disciple under the Bodhi-tree.  More than any other school, Zen stresses the prime importance of the enlightenment experience and the uselessness of ritual religious practices and intellectual analysis of doctrine for the attainment of liberation.  Zen teaches the practice of zazen, sitting in meditative absorption as the shortest, but also the steepest, way to awakening.  

The essential nature of Zen can be summarized in four short statements: 1) "(a) special transmission outside of the orthodox teaching"; (2) non-dependence on sacred writings; and (3) "direct pointing to the human heart:; leading to (4) realization of one's own nature and becoming a buddha".  The pregnant characterization of Zen is attributed by tradition to Bodhidharma, its first patriarch; however, many modern scholars suspect that it originated rather with the later Ch'an master Nan-ch'uan P'u-yuan.  

According to legend the "special transmission outside the orthodox teaching" began with the famous discourse of Buddha Shakyamuni on Vulture Peak Mountain.  At that time, surrounded by a great host of disciples who had assembled to hear him expound the teaching, he is said only to have held up a flower without speaking.  Only his student Kashyapa understood and smiled--as a result of his mater's gesture he suddenly experienced a breakthrough to enlightened vision and grasped the essence of the Buddha's teaching on the spot.  With this, the first transmission from heart-mind to heart-mind took place.  In Zen, which is often also called the "School of Buddha-Mind," sudden enlightenment has played a central role.  

Esoterically regarded, Zen is not a religion but rather an indefinable, incommunicable root, free from all names, descriptions, and concepts, that can only be experienced by each individual for him-or herself.  From expressed forms of this, all religions have sprung.  In this sense Zen is not bound to any religion, including Buddhism.  It is the primordial perfection of everything existing, designated by the most various names, experienced by all great sages, saints, and founders of religions of all cultures and times.  Buddhism has referred to it as the "identity of samsara and nirvana." From this point of view azan is not a "method" that brings people living in ignorance to the "goal" of liberation; rather it is the immediate expression and actualization of the perfection present in every person at every moment.