Diamond Glossary: The Terms That Matter When You Shop
Diamond shopping gets easier once the vocabulary stops sounding mysterious. These are the terms you are most likely to encounter on reports, retailer listings and educational guides.
4Cs
Cut, color, clarity and carat weight—the four standardized categories commonly used to describe diamond quality.
Blemish
A clarity characteristic confined to the surface of a diamond.
Bow tie
A dark bow-shaped contrast zone that can appear across elongated brilliant shapes such as oval, pear and marquise.
Brightness
White light returned from a diamond to the observer.
Carat
A unit of mass equal to 200 milligrams.
Clarity
A grading category describing internal inclusions and surface blemishes.
Cloud
A group of tiny clarity characteristics that can look hazy under magnification.
Crown
The portion of a faceted diamond above the girdle.
Culet
The facet or point at the bottom of the pavilion.
CVD
Chemical vapor deposition, a method used to grow diamond in a laboratory.
Depth percentage
Diamond depth expressed as a percentage of its width or average diameter, depending on shape.
Eye-clean
Retail shorthand for a diamond whose inclusions are not readily visible without magnification; not a laboratory clarity grade.
Facet
A flat polished surface on a cut diamond.
Feather
A common clarity characteristic that is a separation or break within the diamond.
Fire
Colored flashes caused by dispersion of white light.
Fluorescence
Visible light emitted by a diamond when exposed to ultraviolet radiation.
Girdle
The outer edge separating crown from pavilion.
HPHT
High pressure, high temperature; a laboratory diamond growth method and also a term used for certain treatment processes.
Inclusion
An internal clarity characteristic.
Length-to-width ratio
Length divided by width; used to describe the outline proportions of fancy shapes.
Pavilion
The portion of a polished diamond below the girdle.
Polish
A finish grade describing the quality of facet surfaces.
Scintillation
Flashes and contrast patterns seen as diamond, viewer or light source moves.
Simulant
A material that resembles diamond but is not diamond, such as cubic zirconia.
Spread
Informal term for how large a diamond appears face-up for its weight.
Step cut
A faceting style with long, usually parallel facets, seen in emerald and Asscher cuts.
Symmetry
A finish grade describing alignment and balance of facets and outline.
Table
The large flat facet on top of a diamond.
Table percentage
Table width expressed as a percentage of the diamond’s width or average diameter.
Windowing
An area of weak light return that can allow the viewer to see through the diamond, often discussed with step cuts.
Core gemology references: Gemological Institute of America (GIA) diamond education and research materials. Consumer terminology and disclosure principles: U.S. Federal Trade Commission Jewelry Guides. Last reviewed August 2026.