Everyone is familiar with the term "carat" when talking about either gold or precious stones. However, not everyone is aware that carat as applied to gold, means something completely different to carat as applied to diamonds.
In this context, a carat is simply a measurement of weight (1 carat = 0.2 grams). Hence the more carats, the heavier the weight and, other things being equal, the greater the value. Of course, in real life other things never are quite equal, so the value of the stone includes other factors such as clarity, colour, the quality of the cutting, even the country of origin.
If you were wondering where the term carat originated, it derives from "carob" - as in the food ingredient sometimes used instead of chocolate. In ancient times precious stones were measured according to the weight of carob seeds (one carob seed equals one carat).