Clarity is a measure of the number and size of the tiny imperfections that occur in almost all diamonds.
Many of these imperfections are microscopic, and do not affect a diamond's beauty in any discernible way.
Much is made of a diamond's clarity, but of the Four Cs, it is the easiest to understand, and, according to many experts, generally has the least impact on a diamond's appearance. Clarity simply refers to the tiny, natural imperfections that occur in all but the finest diamonds.
Gemologists refer to these imperfections by a variety of technical names, including blemishes and inclusions, among others. Diamonds with the least and smallest imperfections receive the highest clarity grades. Because these imperfections tend to be microscopic, they do not generally affect a diamond's beauty in any discernible way.