In physics, density is mass (m) per unit volume (V) — the ratio of the amount of matter in an object compared to its volume. A small, heavy object, such as a rock or a lump of lead, is denser than a larger object of the same mass, such as a piece of cork or foam.
Depending on its density determines whether or not oil will sink or float on water. Density can also be expressed as Specific_Gravity which is the ratio of the density of the substance as compared to a reference material at a standard set of conditions.
Density is usually expressed as the greek letter 'rho' ().
