The Sun-style (孫氏) t'ai chi ch'uan .
Sun style t'ai chi ch'uan was developed by Sun Lutang, who was considered expert in two other internal martial arts styles: xingyiquan and baguazhang before he came to study t'ai chi ch'uan.
Today, Sun-style ranks fourth in popularity and fifth in terms of seniority among the five family styles of t'ai chi ch'uan. He was also considered an accomplished Neo-Confucian and Taoist
scholar, especially in the Yi Jing and the T'ai chi classics. Sun learned Wu (Hao)-style t'ai chi ch'uan from Hao Weizhen, who was Li Yiyu's (李亦畬) chief disciple.