Real Dictionary

diamond
variable noun: A diamond is a hard, bright, precious stone which is clear and colourless. Diamonds are used in jewellery and for cutting very hard substances.

diamond in American English
a usually colorless, crystalline mineral consisting of pure carbon, with nearly perfect cleavage and the greatest hardness of any substance: unflawed, transparent stones are cut into gems of great brilliance, and less perfect forms are used for cutting to
of, like, or set with a diamond or diamonds
noun: a pure or nearly pure, extremely hard form of carbon, naturally crystallized in the isometric system

diamond in British English
noun: a colourless exceptionally hard mineral (but often tinted yellow, orange, blue, brown, or black by impurities), found in certain igneous rocks (esp the kimberlites of South Africa). It is used as a gemstone, as an abrasive, and on the working edges of cut