Blemish: A flaw, scratch or abrasion on the surface of the gem. Also known as "complexion".

Brilliance: White light reflected up through the surface of a diamond.

Carat: A unit of weight for a diamond ­ the equivalent to 200 milligrams or one-fifth of a gram.

Center Stone: The central, most dominant stone in a piece of jewelry set with multiple stones. It is also known as the solitaire.

Clarity: A grade given to diamond to describe how many inclusions the diamond has. The clarity scale ranges from FL (flawless), meaning no internal or external flaws to severely included (13), meaning a diamond with many clearly visible flaws.

Cloud: A cluster of small inclusions inside a diamond.

Comfort Fit: The rounded finish on a ring's interior, designed to provide additional comfort for long wear.

Culet: The foundation facet of a diamond. The preferred culet is visible only as a tiny focal point where the facets of the bottom portion of the diamond converge.

Color: A grade given to a diamond to describe the color tones of the stone. The color scale ranges from D meaning completely colorless to Z, which has a distinct yellow hue. As the scale moves from D to Z, it indicates increasing levels of yellow and brown tones.

Cut: Commonly used to refer to both the shape of a stone (round, pear, oval heart, etc) and the make (the exact geometric proportions to which a diamond is cut). The make of the stone is the most important factor in determining how much sparkle a diamond produces.

Brilliant Cut: Any cut that utilizes 58 facets. It can be cut to be round, oval, radiant, pear or heart-shaped.

Ideal Cut: Round diamonds that are perfectly proportioned and have high grades on polish and symmetry.

Very Good Cut: Diamonds cut to fit very strict requirements for depth and table percentages and are known for maximizing the fire and brilliance of the diamond.

Good Cut: Diamonds cut with acceptable, but not perfect, cut proportions. Known to have very good brilliance, they make excellent jewelry.

Fair Cut: Diamonds cut to maximize the weight of the stone, generally at the expense of the fire and brilliance. In other words, they have less sparkle.

Depth: The height of a diamond (measured from the culet to table).

Depth Percentage: The height of a diamond divided by the width of the diamond. It is critical to creating brilliance and fire in a diamond.Eye-Clean: A diamond that has no inclusions visible to the unaided eye.

Facet: The flat polished surfaces of a diamond.

Fire: Colored light reflected from within diamond.

Flourescence: A glow, usually of a bluish color which originates from certain diamonds when exposed to ultraviolet light.

Girdle: The narrow band around the width of a diamond.

Head: Attached to the ring shank, the head of the ring holds the center stone in place.

Head Shaped: The shape of the gemstone. For example, the head that holds an ideal-cut is round.Inclusion: Trace minerals, fractures and other imperfections in the stone, which are created during the diamond's formation underground.

Make: The proportions a diamond is cut. A good make will maximize the brilliance and fire of a diamond.Mohs Hardness Scale: A scale to determine the relative hardness of minerals with 1 being the Softest and 10 being the hardest.

Overtone: A hint of another color, which can be blueish, pinkish or silverish.

Pavilion: The bottom portion of the diamond from just below the girdle.

Polish: A grade given to the external finish of a stone.

Sparkle: The amount of light that reflects out of a diamond that creates the fire and brilliance.

Shank: The part of the ring that encircles the finger.

Side Stone: A stone set alongside or encircling a center stone.

Spherical: A round, globular shape.

Symmetry: A grade given to the overall uniformity of a stone's cut with a scale ranging from poor to excellent. Poor symmetry will hurt the sparkle of a diamond.

Table: Located on the top of a diamond facing out from the setting, it is the largest facet on a diamond.

Table Percentage: The width of the table divided by the total diameter of the diamond.Thickness: The measurement, in millimeters, that indicates the width of the ring band or shank.