a unit for measuring the weight of diamonds and other precious stones, equal to 200 milligrams 克拉（钻石或其他宝石的重量单位，等于 200 毫克） - (especially British English) (North American English usually karat)
a unit for measuring how pure gold is. The purest gold is 24 carats 开（黄金成色单位，纯金为 24 开） an 18-carat gold ring 18 开的金戒指
Word Originlate Middle English (in sense (2)): from French, from Italian carato, from Arabic qīrāṭ (a unit of weight), from Greek keration ‘fruit of the carob tree’ (also denoting a unit of weight), diminutive of keras ‘horn’, with reference to the elongated seed pod of the carob.