Diamonds can have cut grades of Ideal, Very Good, Good, Fair, and Poor. The cut, or proportions and angles, of a diamond determines how it reflects light. A diamond's reflective properties are referred to as "fire" or "brilliance." Too shallow a cut will let light escape through the sides of the diamond before it has a chance to reflect, making it appear watery or dull, while too deep a cut will allow light to be lost through the bottom of the diamond, making it appear dark, especially in the center.