The nearest smaller commonSI unit is thenanometre, equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (0.000000001 m).
The termmicron andthe symbol μ were officially accepted for use in isolation to denote the micrometre in 1879, but officially revoked by theInternational System of Units (SI) in 1967.[9] This became necessary because the older usage was incompatible with the official adoption of the unit prefixmicro-, denoted μ, during the creation of the SI in 1960.
In the SI, the systematic namemicrometre became the official name of the unit, and μm became the official unit symbol.
InAmerican English, the use of "micron" helps differentiate the unit from themicrometer, a measuring device, because the unit's name in mainstreamAmerican spelling is ahomograph of the device's name. In spoken English, they may be distinguished by pronunciation, as the name of the measuring device is often stressed on the second syllable (/maɪˈkrɒmɪtər/my-KROM-it-ər), whereas the systematic pronunciation of the unit name, in accordance with the convention for pronouncing SI units in English, places the stress on the first syllable (/ˈmaɪkroʊmiːtər/MY-kroh-meet-ər).[original research?]
The plural ofmicron is normallymicrons, thoughmicra was occasionally used before 1950.[10][11][12]
Beforedesktop publishing became commonplace, it was customary to render the symbol μ in texts produced with mechanicaltypewriters by combining a slightly lowered slash with the letteru. For example, "15 μm" would appear as "15/um". This gave rise in earlyword processing to substituting just the letteru for the symbol if the Greek letter μ was not available, as in "15 um".[15]
The UnicodeCJK Compatibility block contains square forms of some Japanesekatakana measure and currency units.U+3348㍈SQUARE MIKURON corresponds toミクロンmikuron.
^"Wool Fibre".NSW Department of Education and Communities. Archived fromthe original(Word Document download) on 17 June 2016. Retrieved18 May 2014.
^Ramel, Gordon."Spider Silk".Archived from the original on 4 December 2008. Retrieved14 December 2008.A typical strand of garden spider silk has a diameter of about 0.003 mm ... Dragline silk (about .00032 inch (.008 mm) inNephila)
^"Fibreshape applications". IST - Innovative Sintering Technologies Ltd. Retrieved4 December 2008.Histogram of Fiber Thickness [micrometre]
^Thediameter of human hair ranges from 17 to 181 μm.Ley, Brian (1999). Elert, Glenn (ed.)."Diameter of a human hair".The Physics Factbook. Retrieved8 December 2018.
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