BijanDiamonds.com Dictionary
Carat Weight:
The weight of a diamonds is generally given in carats. Carat (ct.) is the standard unit of weight used for gemstones. 1.00 carat is equal to 0.20 grams or 200 milligrams.

Diamonds are weighed to a thousandth (0.001) of a carat and then rounded to the nearest hundredth, which is called point. Over a carat, diamond weights are usually expressed in carats and decimals. A 1.05 ct. stone, for example, would be described as "one point oh five carats" or "one oh five." A diamond that weighs 0.73 ct. is said to weigh "seventy-three points," or an "seventy-three pointer."