T’ai chi ch’uan or Taijiquan, often shortened to t’ai chi, taiji or tai chi in English usage, is an internal Chinese martial art practiced for both its defense training and its health benefits. It is also typically practiced for a variety of other personal reasons: its hard and soft martial art technique, demonstration competitions, and longevity. As a result, a multitude of training forms exist, both traditional and modern, which correspond to those aims. Some of t’ai chi ch’uan’s training forms are especially known for being practiced at what most people categorize as slow movement. Today, t’ai chi ch’uan has spread worldwide. Most modern styles of t’ai chi ch’uan trace their development to at least one of the five traditional schools: Chen, Yang, Wu (Hao), Wu, and Sun.