The quantity of "matter" contained in an object, given by

(1)

where is the density. The cgs unit of mass is the gram, the MKS unit the kilogram, and the foot-pound-second unit is the slug. Note that the pound is not a unit of mass, but rather one of weight. While no less an authority than the National Institute of Standards and Technology notes that "in commercial and everyday one, and especially in common parlance, weight is usually used as a synonym for mass" (Taylor 1995, p. 24), this extremely confusing practice should be universally discouraged.

The term "mass" is commonly confused with weight. However, whereas mass is an inherent property of a body, weight

(2)

is the product of mass m by the gravitational acceleration g (this formula is a special case of Newton's second law), and therefore depends on the strength of gravitational acceleration to which a body is subjected. The weight of a body would therefore be less at the top of a mountain than at the mountain's foot.

Apdram, Apounce, Appound, Atomic Mass Unit, Density, Force, Grain, Gram, Inertia, Kilogram, Mass Increase, Matter, Momentum, Newton's Second Law, Pound-Mass, Quintal, Relativistic Mass, Rest Mass, Scruple, Slug, Troy System of Units, Weight