Definition: Density is also called mass density and designates the quotient from the mass of a body as well as its volume.
The density of fluids plays an important role in the delivery. The density of fluids depends on the atmospheric pressure and the temperature. Substances typically expand with increasing temperature; one exception is water.
The mass density is often given in kilogram per cubic meter (kg/m³), in case of fluids also in kilogram per liter (kg/l).