Dictionary · Standards & Units
System of units
A set of base and derived units, with their multiples and submultiples, defined under given rules for a given system of quantities.
Related terms
More from Standards & Units
Measurement standard (etalon)
The realization of the definition of a given quantity, with stated value and uncertainty, used as a reference — an artifact, instrument, reference material, or measuring system.
VIM (JCGM 200:2012) 5.1
System of quantities
A set of quantities together with the non-contradictory equations relating them — the framework a system of units is built on.
VIM (JCGM 200:2012) 1.3
International System of Units (SI)
The system of units based on the ISQ, with unit names, symbols, prefixes, and rules for their use, adopted by the CGPM. Since the 2019 revision all seven base units are defined by fixing the numerical values of seven defining constants.
VIM (JCGM 200:2012) 1.16
Ordinal quantity-value scale
A quantity-value scale for ordinal quantities, established by agreement on a procedure — comparisons of order are valid, arithmetic on the values is not.
VIM (JCGM 200:2012) 1.28
Ordinal quantity
A quantity defined by an agreed procedure that can be ranked but has no meaningful algebra — Rockwell hardness or earthquake magnitude: order exists, differences and ratios do not.
VIM (JCGM 200:2012) 1.26
Secondary measurement standard
A standard established through calibration with respect to a primary standard for a quantity of the same kind.
VIM (JCGM 200:2012) 5.5