Wok hei is a term in referring to the flavour, tastes, and "essence" imparted by a hot wok on the food. The word ''hei'' is equivalent to ''qi'' . The term is sometimes rendered as ''wok chi'' in Western cookbooks.
When cooked correctly, the "essence" of the food comes through the flavour and the dish is said to "have ''wok hei''". To impart ''wok hei'', the food must be cooked in a wok over a high flame while being stirred and tossed quickly. In practical terms, the flavour imparted by chemical compounds results from caramelization, Maillard reactions, and the partial combustion of oil that come from charring and searing of the food at very high heat in excess of 200 °C . According to the Professional Chef, a textbook for the Culinary Institute of America, stir fry technique does not require as much fat as typical western dishes because of a combination of the metal type and the constant shifting of the food during cook time. As diners usually elect their food with chopsticks from a shared serving bowl, any excess oil remains in the bottom of the serving dish rather than being eaten.