Diameter: The diameter is the width of the diamond as measured through the girdle.
Table: The table is the flat facet on the top of the diamond. It is usually the largest facet on a cut diamond. The table also plays a role in determining sparkle and fire.
Table Percentage: The table percentage is the value which corresponds to how the diameter of the table facet compares to the diameter of the entire diamond. For example, a stone that has 50% table has a table which is a 50% as wide as the diameter of the diamond. In terms of finding the table percentage of a round stone, gemologists usually calculate the table percentage by dividing the diameter of the table by the average girdle diameter.
Crown: The crown is the upper part of the diamond that lies above the girdle. The crown determines the scintillation, or sparkle of the diamond, as well as the fire, or dispersion.
Girdle: The girdle is the outer edge and the widest part around the diamond. The girdle forms a band around the stone and protects it from chipping. At times, the girdle could be too thick and add unnecessary weight to the stone.
Pavilion: The pavilion lies at the bottom part of the diamond, below the girdle. It plays the most important role in determining the brilliance.
Culet: The culet is the final facet to be polished on the diamond. It is a tiny final facet that diamond cutters often add at the bottom of the diamond's pavilion. The purpose of the culet is to protect the tip of the pavilion from being damaged. After the diamond is set in jewelry, the actual setting provides the pavilion with enough protection. However, modern shapes rarely have a culet at all, or a very small one.
Depth: The depth refers to the height of the stone from the culet to the table. It is usually measured in millimeters.
Facet: The facets are the flat, smooth faces on the surface of the diamond. A facet allows light to enter the diamond as well as reflect off its surfaces from the different angles. They aid in creating the different colors and light that diamonds are known for.