Bok choy or pak choi (Chinese: 青菜; Brassica rapa subsp. chinensis) is a type of Chinese cabbage. Chinensis varieties do not form heads; instead, they have smooth, dark green leaf blades forming a cluster reminiscent of mustard or celery.Chinensis varieties are popular in southern China and Southeast Asia.ther than the ambiguous term Chinese cabbage, the most widely used name in North America for the chinensis variety is bok choy (from Cantonese, literally white vegetable; also spelled pak choi, bok choi, and pak choy).