Dictionary · Standards & Units
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.
Related terms
More from Standards & Units
Conventional reference scale
A quantity-value scale defined by formal agreement — pH and the practical temperature scales are canonical examples.
VIM (JCGM 200:2012) 1.29
Multiple of a unit
A unit obtained by multiplying a given unit by an integer greater than one — the kilometre from the metre.
VIM (JCGM 200:2012) 1.17
Derived unit
A measurement unit for a derived quantity, formed as a product of powers of base units — the newton (kg·m·s⁻²) or the pascal (N/m²).
VIM (JCGM 200:2012) 1.11
Transfer measurement device
A device used as an intermediary to compare measurement standards — transferring, not holding, the quantity value.
VIM (JCGM 200:2012) 5.9
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.
VIM (JCGM 200:2012) 1.13
Quantity dimension
The expression of a quantity's dependence on the base quantities as a product of powers of their dimensions — force has dimension L·M·T⁻².
VIM (JCGM 200:2012) 1.7