Carat
The weight of diamonds is one of the elements which set their price, along with their size, colour and purity. Weight is measured to the closest hundreth and the carat is divided in 100 points. A quarter of a carat is referred to as a 25-point whereas a 50-point refers to a half-carat.
A diamond's price evolves exponentially according to its weight and is established by threshold. Therefore, it is possible for a 0.98 carat (98-point) diamond's price to be much different than that of a 1.00 carat (100-point) diamond, since these two values are part of two distinct thresholds. Moreover, considering the rarity of large gems, the price of such gems is not proportional to their weight: a 1.50 carat diamond weighs three times more than a 0.5 carat diamond (50 points), but its price may be between 5 and 7 times higher.