Dictionary · Standards & Units
Coherent derived unit
A derived unit that is a product of powers of base units with no numerical factor other than one — the newton is coherent in the SI; the kilometre per hour is not.
Related terms
More from 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.
VIM (JCGM 200:2012) 1.16
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
Numerical quantity value
The number in a quantity value — the 5.34 in 5.34 m: the ratio of the quantity to its unit.
VIM (JCGM 200:2012) 1.20
Reference quantity value
A quantity value used as a basis for comparison with values of quantities of the same kind — a true value, a conventional value, or a standard's certified value, depending on context.
VIM (JCGM 200:2012) 5.18
Numerical value equation
A relation between numerical values that holds only for stated units — the form most spreadsheet formulas quietly are, and the reason unit discipline matters.
VIM (JCGM 200:2012) 1.25
Quantity of dimension one
A quantity whose dimension has all base-quantity exponents equal to zero — refractive index, strain, a ratio of like quantities; often loosely called "dimensionless".
VIM (JCGM 200:2012) 1.8