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Planck units is system of geometrized units in which the reduced Planck constant is included in the list of defining constants. It is based on only properties of free space rather than of any object or particle. Stoney units is a system of geometrized units in which the Coulomb constant and the elementary charge are included.
The metre, kilogram, second system of units, also known more briefly as MKS units or the MKS system, [1] [2] [3] is a physical system of measurement based on the metre, kilogram, and second (MKS) as base units. Distances are described in terms of metres, mass in terms of kilograms and time in seconds.
The International System of Units, internationally known by the abbreviation SI (from French Système international d'unités), is the modern form of the metric system and the world's most widely used system of measurement. It is the only system of measurement with official status in nearly every country in the world, employed in science ...
The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram).
In metrology (the science of measurement), a standard (or etalon) is an object, system, or experiment that bears a defined relationship to a unit of measurement of a physical quantity. [1] Standards are the fundamental reference for a system of weights and measures , against which all other measuring devices are compared.
The United States system of units of 1832 is based on the system in use in Britain prior to the introduction to the British imperial system on January 1, 1826. [6] Both systems are derived from English units, a system which had evolved over the millennia before American independence, and which had its roots in both Roman and Anglo-Saxon units.
The metric system is a decimal system of measurement based on its units for length, the metre and for mass, the kilogram. It exists in several variations, with different choices of base units, though these do not affect its day-to-day use. Since the 1960s, the International System of Units (SI) is the internationally recognised metric system.
The imperial system of measure does not have an equivalent to the US customary system of "dry measure". In the international commodities markets, the barrel ( 42 US gallons , ≈159 litres) is used in both London and New York/Chicago for trading in crude oil and the troy ounce (≈31.10 grams) for trading in precious metals, except the London ...