Bok choy

Bok choy (also known as pak choi, boc choy, and pok choi) is classified as a Chinese cabbage. It is part of the cabbage family and does not have the same stringiness. The dark green, crinkly leaves of the most common type are like Romaine lettuce. 
History.
The Chinese, who have been cultivating the plant for more than 5000 years, commonly refer to bok choy as pak choi or "white vegetable." Another common name is white cabbage.