In the "four Cs" of diamonds, cut refers to the way a diamond has been shaped and faceted to reflect light and create its characteristic sparkle. The cut of a diamond is a crucial factor that affects its overall beauty, as it determines how well the diamond interacts with light, and how much it sparkles and reflects.

A diamond's cut is determined by the quality of the diamond cutter's work and the proportions, symmetry, and polish of the diamond's facets. A well-cut diamond will reflect the maximum amount of light, creating a bright and sparkling appearance. On the other hand, a poorly cut diamond will appear dull and lifeless.

When evaluating a diamond's cut, important factors to consider include the diamond's symmetry, proportion, and polish. The cut of a diamond is graded on a scale that ranges from Excellent to Poor, with Excellent being the highest quality and Poor being the lowest.