Nappa cabbage (also: NAPA cabbage, Chinese leaves, Chinese cabbage, Wombok, Baechu, Celery cabbage, Chinese celery cabbage, Peking cabbage, wong bok, petsai, shantung cabbage, hakusia, michihli and confusingly sometimes even bok choy) is a family of cabbages (Brassica campestris, Pekinensis group) used in Chinese and Korean cuisine. The cabbage head is tightly packed, taller than it is wide, and very light green with white near the base.
The name may be of Japanese origin or may be a Chinese word first exposed to English speakers through Japan. The Japanese script is: 菜っ葉 for Chinese cabbage, (in Japan, it is a generic term for leaf vegetables.)
Nappa cabbage is commonly used as cheap filler for egg rolls (spring rolls), wontons, and chow mein. It makes for a good vegetable addition to stir fries. It can be used as a milder and more delicate alternative to green cabbage. Bok choy, green cabbage or savoy cabbage can be substituted for nappa cabbage but these will have a stronger flavor and take longer to cook.
It is also the main ingredient in the most popular version of kimchi, although many varieties of kimchi do not require cabbage.