Dictionary · Standards & Units
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.
Related terms
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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.
VIM (JCGM 200:2012) 1.12
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
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
Travelling measurement standard
A standard, sometimes of special construction, intended for transport between locations — the artifacts that carry interlaboratory comparisons.
VIM (JCGM 200:2012) 5.8
Kind of quantity
The aspect common to mutually comparable quantities — length, mass, and energy are kinds; diameter and wavelength are both quantities of the kind length.
VIM (JCGM 200:2012) 1.2
Submultiple of a unit
A unit obtained by dividing a given unit by an integer greater than one — the millimetre from the metre.
VIM (JCGM 200:2012) 1.18