CHI

I. noun Etymology: Greek chei, ~ Date: 15th century the 22d letter of the Greek alphabet, II. noun or ch'i; also qi Usage: often capitalized Etymology: Chinese (Beijing) qì, literally, air, breath Date: 1850 vital energy that is held to animate the body internally and is of central importance in some Eastern systems of medical treatment (as acupuncture) and of exercise or self-defense (as tai ~)