Density is defined as mass per unit volume. The symbol most commonly used for density is ρ (the lower case Greek letter rho). The capital letter D is also used. Density is an intensive property of matter, which means the size of a sample does not affect its value. Density commonly is expressed in units of grams per milliliter and kilograms per liter.
The equation for density is:
density = mass / volume
ρ = m/V
The reciprocal of density (V/m) is its specific volume.
Density tends to be higher for solids than for liquids, which are in turn more dense than gases. The density of pure water is defined to be 1 gram per milliliter.