The design and craftsmanship of the diamond considers weight ratio (weight of the diamond relative to its diameter), the diamond's girdle thickness (which affects its durability), the symmetry of its facet arrangement, and the quality of polish on those facets.
Cut is often times confused with the shape of the diamond but cut refers to a stone’s facet arrangement. Shape refers to the outline of the stone. The most common diamond shape used in jewelry is round, as seen in the standard round brilliant cut. All other diamond shapes are known as fancy shapes. Traditional fancy shapes include the marquise, pear, oval and octagonal (as seen in the emerald cut). Square, cushion (square with rounded edges), triangle, and a variety of other shapes are also gaining popularity in diamond jewelry.