Minerals (from medieval Latin mineral, derived from ancient French mining, “mine”) are inorganic and natural bodies, with a well-defined or variable chemical composition within a narrow range; they make up the earth's crust and other celestial bodies. They are all solid (except native mercury). They have constant physical and chemical properties, which allow them to be identified and distinguished from one another. In the historical context, the expression mineral kingdom referred to all inanimate objects, mainly minerals and rocks, according to Linnaeus' Systema Naturae.

The term today, correctly understood in the scientific sense, is more restrictive and designates chemical compounds of natural origin, that is to say bodies which have a defined or variable chemical composition within the very precise limits imposed by stoichiometry; they are almost always in crystalline form, are solid at room temperature (with the exception of native mercury and ice) and predominantly inorganic.