The weight of a diamond is measured in “Carat”. The carat of a diamond denotes its size.
The word “carat” has been derived from the word the carob seeds which people used in to weigh their balance scales. The short form of carat is “CT” and “TCW” stands for total carat weight.
A carat includes 100 'points’ and a jeweler defines the weight of a diamond below a carat by its “points”. Supposedly, if a diamond weighs 0.40 carats it is thereby declared as a “forty pointer.”