Definition from Wiktionary, the free dictionary
Alternative forms 
- (unit of purity): karat (North America)
carat (plural carats)
- A unit of weight for precious stones and pearls, equivalent to 200 milligrams.
- Formerly, any of several units of weight, varying from 189 to 212 mg, the weight of a carob seed.
- A measure of the purity of gold, pure gold being 24 carats.
measure of the purity of gold