Carat - Weight measurement used in reference to gemstones in regard to their evaluation. A carat is .2 grams (or 200 milligrams), and this weight is used worldwide, even in the U.S. where the metric system isn't used. A point is the weight used only in reference to very small, precious gemstones, and represents 1/100^th of a carat. The abbreviation for carat is Ct. and for point is Pt.
The term carat in regard to gemstones should not be confused with the term carat in regard to gold. By gold, it refers to the content of gold a gold ornament contains. Because of the confusion, the term carat in regard to gold has been changed to karat. (See karat)