The nearest smaller common SI unit is the nanometre, equivalent to one thousandth of a micrometre, one millionth of a millimetre or one billionth of a metre (0.000000001m).
The term micron and the symbol μ were officially accepted for use in isolation to denote the micrometre in 1879, but officially revoked by the International System of Units (SI) in 1967.[8] This became necessary because the older usage was incompatible with the official adoption of the unit prefix micro-, denoted μ, during the creation of the SI in 1960.
In the SI, the systematic name micrometre 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 the micrometer, a measuring device, because the unit's name in mainstream American spelling is a homograph 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).
The plural of micron is normally microns, though micra was occasionally used before 1950.[9][10][11]
Before desktop publishing became commonplace, it was customary to render the symbol μ in texts produced with mechanical typewriters by combining a slightly lowered slash with the letter u. For example,『15 μm』would appear as "15/um". This gave rise in early word processing to substituting just the letter u for the symbol if the Greek letter μ was not available, as in "15 um".[14]
The Unicode CJK Compatibility block contains square forms of some Japanese katakana 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 from the original(Word Document download) on 17 June 2016. Retrieved 18 May 2014.
^Ramel, Gordon. "Spider Silk". Archived from the original on 4 December 2008. Retrieved 14 December 2008. A typical strand of garden spider silk has a diameter of about 0.003 mm ... Dragline silk (about .00032 inch (.008 mm) in Nephila)
^"Fibreshape applications". IST - Innovative Sintering Technologies Ltd. Retrieved 4 December 2008. Histogram of Fiber Thickness [micrometre]
^The diameter of human hair ranges from 17 to 181 μm. Ley, Brian (1999). Elert, Glenn (ed.). "Diameter of a human hair". The Physics Factbook. Retrieved 8 December 2018.
The dictionary definition of micrometre at Wiktionary
