The Carat corresponds to the weight of the diamond and therefore also to its size.
The carat corresponds to 200 milligrams. In fact, diamonds are weighed and certified to the hundredth of a carat with special sensitive electronic scales.
Then there is the Emerald cut of rectangular shape with rounded corners, as well as the square or heart-shaped, or baguette or oval.
The name carat is said to refer to the seed of the carob tree which by nature is always produced in identical specimens and which in the Indies was precisely used for weighing precious stones.
For obvious understandable reasons the diamond of greater weight and therefore of greater size has in itself an increase significantly higher degree of rarity which then determines its value.