The cut of a diamond refers to the way the stone is shaped and polished, how the facets are arranged and how deep or shallow it's cut. There are various cuts of diamonds that refer to that, many of them patented. Both Asscher and Princess diamonds are square-shaped diamonds, but they are vastly different in how the facet are cut and arranged.

Cut also refers to the shape of the diamond. The shape is often determined by how the molecules of the crystal are arranged. If it's an octahedron, it will be cut as a round brilliant, and often two round brilliants can be cut from the same original crystal. Other crystal configurations, such as macer, will be cut as marquise or oval diamonds.

The modern round cut brilliant stone has 58 facets, or 57 if the tiny bottom facet, the culet, is omitted. The Princess cut is unique in that it's a square diamond with pointed corners. Many diamonds, even square and emerald cut diamonds will have rounded or cut-off corners, because contrary to popular opinion, a diamond can chip or scratch if it knocks against something at the wrong angle. It's a bad idea to try to scratch a mirror with any diamond!

An emerald shaped diamond is a rectangle cut with longer, flat facets. It's a good cut for a diamond that's exceptionally clear. If it's not, then an emerald cut diamond can appear cloudy.

The Asscher diamond is similar to an emerald shape, except it's square. It's cutting resembles a spider web when viewed from above.

Other diamond shapes are self-explanatory. A pear- or tear-shaped diamond is exactly that. It's an oval that's wider at one end and curves to a point at the other end. An oval is a perfect oval. The marquise-shaped diamond can maximize the carat weight of a stone because it's a longer and flatter cut, yet highly faceted. The marquise comes in a variety of length-to-width ratios.