a unit of weight used for precious stones equal to 200mg
(NAmer chiefly karat) a unit of fineness for gold equal to one twenty-fourth part of pure gold in an alloy
[French carat, prob via medieval Latin from Arabic qīrāt bean pod, a small weight, from Greek keration carob bean, a small weight, dimin. of kerat-, keras horn; referring to the long seed pod of the carob]