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The prefix symbols are always prepended to the symbol for the unit without any intervening space or punctuation. [9] This distinguishes a prefixed unit symbol from the product of unit symbols, for which a space or mid-height dot as separator is required. So, for instance, while 'ms' means millisecond, 'm s' or 'm·s' means metre-second.
However, the names of all SI mass units are based on gram, rather than on kilogram; thus 10 3 kg is a megagram (10 6 g), not a *kilokilogram. The tonne (t) is an SI-compatible unit of mass equal to a megagram (Mg), or 10 3 kg. The unit is in common use for masses above about 10 3 kg and is often used with SI prefixes.
For historical reasons, the names and symbols for multiples and sub-multiples of the unit of mass are formed as if the gram were the base unit. Prefix names and symbols are attached to the unit name gram and the unit symbol g respectively. For example, 10 −6 kg is written milligram and mg, not microkilogram and μkg. [1]: 144
The fermi is a unit of distance used in nuclear physics equal to 1 fm. [9] The angstrom (symbol Å) is a unit of distance used in chemistry and atomic physics equal to 100 pm. The micron (μ) is a unit of distance equal to one micrometre (1 μm). The basic module (M) is a unit of distance equal to one hundred millimetres (100 mm).
The prefixes of the metric system precede a basic unit of measure to indicate a decadic multiple and fraction of a unit. Each prefix has a unique symbol that is added to the beginning of the unit symbol. Some of the prefixes date back to the introduction of the metric system in the 1790s, but new prefixes have been added, and some have been ...
Conversions between units in the metric system are defined by their prefixes (for example, 1 kilogram = 1000 grams, 1 milligram = 0.001 grams) and are thus not listed in this article. Exceptions are made if the unit is commonly known by another name (for example, 1 micron = 10 −6 metre).
Micro (Greek letter μ, mu, non-italic) is a unit prefix in the metric system denoting a factor of 10 −6 (one millionth). [1] It comes from the Greek word μικρός (mikrós), meaning "small". [2] It is the only SI prefix which uses a character not from the Latin alphabet.
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.