Language:enStatus: Standard
Term: value of a quantity
Synonym1: quantity value
Synonym2: value
Definition: number and reference together expressing magnitude of a quantity

Note 1 to entry: According to the type of reference, the value of a quantity is either:

  1. a product of a number and a unit of measurement (the unit one is generally omitted for quantities of dimension one, as in examples f and g):

    a) Length of a given rod: 5,34 m or 534 cm

    b) Mass of a given body: 0,152 kg or 152 g

    c) Curvature of a given arc: 112 m–1, expressed in words by "one hundred and twelve per metre"

    d) Celsius temperature of a given sample: –5 C

    e) Electric impedance of a given circuit element at a given frequency, where j is the imaginary unit: (7,5 + 3,2 j) Ω

    f) Refractive index of a given sample of glass: 1,32

    g) Mass fraction of cadmium in a given sample of copper: 3 g/kg or 3 10–1

    h) Molality of Pb2+ in a given sample of water: 1,76 mmol/kg

  2. a number and a reference to a measurement procedure:

    Rockwell C hardness of a given sample: 43,5 HCR

  3. a number and a reference material:

    Arbitrary amount-of-substance concentration of lutropin in a given sample of human blood plasma (WHO International Standard 80/552 used as a calibrator): 5,0 IU/l, where "IU" stands for "WHO International Unit"

In the first case, the value of a quantity Q is generally denoted {Q}[Q] where {Q} is the numerical value and [Q] is the unit of measurement.

Note 2 to entry: The number can be complex (see example e in Note 1 to entry).

Note 3 to entry: The value of a quantity can be presented in more than one way (see examples a, b, and g in Note 1 to entry).

Note 4 to entry: In the case of vector or tensor quantities, each component has a value, and the same for the magnitude of a vector quantity. Example:

force acting on a given particle, e.g. in Cartesian components
(Fx; Fy; Fz) = (–31,5; 43,2; 17,0) N

Publication date:2019-01
SourceISO/IEC Guide 99:2007, 1.19, modified – Transposition of the English preferred term and synonym. Combination of EXAMPLE 1 to EXAMPLE 10 in a new Note 1 to entry, and deletion of NOTE 1.
Internal notes:
CO remarks:
TC/SC remarks:
VT remarks: