bok choy also pak choi 
(bŏk choi)
(bŏk choi)n.
A plant (Brassica rapa subsp. chinensis) in the mustard family, having a loose head of dark green leaves with thick white stems and eaten as a vegetable in eastern Asian cuisine. Also called Chinese cabbage.
[Cantonese baak6 coi3, from Middle Chinese pɦaːjk tshaj` (also the source of Mandarin báicài) : pɦaːjk, white + tshaj`, vegetable.]
bok choyBrassica rapa
subsp. chinensis