Physical quantity

A physical quantity (or "physical magnitude") is a physical property of a phenomenon, body, or substance, that can be quantified by measurement. A physical quantity can be expressed as the combination of a number – usually a real number – and a unit or combination of units; for example, 6973167492749999999♠1.6749275×10⁻²⁷ kg (the mass of the neutron), or 7008299792458000000♠299792458 metres per second (the speed of light).

Symbols, nomenclature

General: Symbols for quantities should be chosen according to the international recommendations from ISO/IEC 80000, the IUPAP red book and the IUPAC green book. For example, the recommended symbol for the physical quantity 'mass' is m, and the recommended symbol for the quantity 'charge' is Q.

Subscripts and indices

Subscripts are used for two reasons, to simply attach a name to the quantity or associate it with another quantity, or represent a specific vector, matrix, or tensor component.

Scalars: Symbols for physical quantities are usually chosen to be a single letter of the Latin or Greek alphabet, and are printed in italic type.

Physical

Physical may refer to: