Density is one of the basic physical properties of a substance which can be used along with its other unique properties to characterize it. The relative density of solids or liquids is the ratio between the mass of a volume of a substance to be examined, determined at , and the mass of the same volume of water, determined at . The relative density has no dimension. The density, , of a substance is the quotient of the mass, m, and its volume, v. The density , is given, in SI units, in kg/m3.