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A unit of measurement, or unit of measure, is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. [1] Any other quantity of that kind can be expressed as a multiple of the unit of measurement. [2] For example, a length is a physical quantity.
The Unified Code for Units of Measure (UCUM) is a system of codes for unambiguously representing measurement units. Its primary purpose is machine-to-machine communication rather than communication between humans. [ 1 ]
Metric units are units based on the metre, gram or second and decimal (power of ten) multiples or sub-multiples of these. According to Schadow and McDonald, [1] metric units, in general, are those units "defined 'in the spirit' of the metric system, that emerged in late 18th century France and was rapidly adopted by scientists and engineers.
List of metric units – Class of units of measurement; Metrology – Science of measurement and its application; Non-SI units mentioned in the SI – Unit accepted for use in the International System of Units; Outline of metrology and measurement – Topical index of English Wikipedia articles about metrology and measurement
The measurement of time is unique in SI in that while the second is the base unit, and measurements of time smaller than a second use prefixed units smaller than a second (e.g. microsecond, nanosecond, etc.), measurements larger than a second instead use traditional divisions, including the sexagesimal-based minute and hour as well as the less ...
SI base units Name Symbol Measure Post-2019 formal definition [1] Historical origin / justification Dimension symbol; second: s time "The second, symbol s, is the SI unit of time.
6 volumetric measures from the mens ponderia in Pompeii, a municipal institution for the control of weights and measures (79 A. D.). A unit of volume is a unit of measurement for measuring volume or capacity, the extent of an object or space in three dimensions.
In antiquity, systems of measurement were defined locally: the different units might be defined independently according to the length of a king's thumb or the size of his foot, the length of stride, the length of arm, or maybe the weight of water in a keg of specific size, perhaps itself defined in hands and knuckles.