I. carat
variant of karat
II. car·at ˈker-ət, ˈka-rət noun
Etymology: Middle English carrat measure of fineness in gold, from Middle French carat measure of fineness in gold or of weight in gems, from Italian carato, from Arabic qīrāṭ bean pod, a small weight, from Greek keration carob bean, a small weight, from diminutive of kerat-, keras horn — more at horn
Date: 1555
: a unit of weight for precious stones equal to 200 milligrams