The word carat was derived from the carob seed, each carob seed weighs very close to 1 carat.

The carat is the weight or mass of a diamond. 5 carats are equal to one gram. One carat is divided into one hundred points, therefore a 25 point diamond is a ¼ carat. Although size is the most obvious factor in determining the value of a diamond, 2 diamonds of equal size can have very unequal values depending on the other 3 properties.