Mass per unit of volume of a substance. I.E. grams/cu.cm. or pounds/cu.ft.
Measure of the compactness of a substance; it is equal to its mass per unit volume and is measured in kg per cubic meter/lb per cubic foot. Density is a scalar quantity. The density D of a mass m occupying a volume V is given by the formula:
D = m/V
Relative density is the ratio of the density of a substance to that of water at 4şC.
In photography, density refers to the degree of opacity of a negative; in population studies, it is the quantity or number per unit of area; in electricity, current density is the amount of current passing through a cross-sectional area of a conductor in a given amount of time (usually given in amperes per sq in or per sq cm).