density science definition

A measure of the quantity of some physical property (usually mass) per unit length, area, or volume (usually volume).
♦ Mass density is a measure of the mass of a substance per unit volume. Most substances (especially gases such as air) increase in density as their pressure is increases or as their temperature decreases.
♦ energy density is a measure of the amount of energy (often in the form of electromagnetic radiation) per unit volume in a region of space or some material. See also Boyle's law.