There are many shapes including the popular Round Brilliant, Radiant and Princess shapes. Measurements are provided in millimeters to the hundredth of a millimeter and include length, width and depth. These measurements are taken with a millimeter gauge especially designed for measuring gems and jewelry. It is very unlikely that anyone could find another diamond with the same three dimensions expressed to the hundredth of a millimeter. Weight of a diamond is expressed in carats.
Proportions describe various parts of the diamond in relation to other parts of the diamond.
The girdle is the thin rim that separates the crown of the stone from the pavilion and is described in words that range from thin to extremely thick. The Culet is the little facet at the very bottom of the stone and can range from large to non-existent. Large culets are generally considered unacceptable. Finish indicates the grade of polish and symmetry of the stone. The symmetry describes how well the facets in the crown are aligned with the facets in the pavilion.