Micrometre#SI standardization

File:How big is 1 micrometer? (10690468113).jpg

Between 1 μm and 10 μm:

• 1–10 μm – length of a typical bacterium
• 3–8 μm – width of strand of spider web silk{{cite web|url=http://www.earthlife.net/chelicerata/silk.html|title=Spider Silk|author=Ramel|first=Gordon|archive-url=https://web.archive.org/web/20081204080140/http://www.earthlife.net/chelicerata/silk.html|archive-date=4 December 2008 |url-status=live|access-date=14 December 2008|quote=A typical strand of garden spider silk has a diameter of about 0.003 mm ... Dragline silk (about .00032 inch (.008 mm) in Nephila)}}
• 5 μm – length of a typical human spermatozoon's head{{cite journal|last1=Smith|first1=D.J.|last2=Gaffney|first2=E.A.|last3=Blake|first3=J.R.|last4=Kirkman-Brown|first4=J.C.|title=Human sperm accumulation near surfaces: a simulation study|url=http://eprints.maths.ox.ac.uk/860/1/human_sperm.pdf|journal=Journal of Fluid Mechanics|publisher=Cambridge University Press|date=25 February 2009|volume=621|pages=295|bibcode=2009JFM...621..289S|doi=10.1017/S0022112008004953|s2cid=3942426|archive-url=https://web.archive.org/web/20131106030353/http://eprints.maths.ox.ac.uk/860/1/human_sperm.pdf|archive-date=6 November 2013|url-status=dead}}
• 6–8 μm – diameter of a typical red blood cell{{Cite web |title=Red Blood Cell (RBC) Size Variation |url=https://www.labce.com/spg579126_red_blood_cell_rbc_size_variation.aspx?srsltid=AfmBOopoMxeqbMEfcE32IWxPyhuaqRGeUXTj2QIKupNwUAMGxIpO3UXV |access-date=2025-02-20 |website=www.labce.com}}
• 10 μm – size of fungal hyphae
• about 10 μm – size of a fog, mist, or cloud water droplet

{{For|more examples of things measuring 1 to 10 micrometres|Orders of magnitude (length)#1 micrometre}}

Between 10 μm and 100 μm:

• about 10–12 μm – thickness of plastic wrap (cling wrap)
• 10 to 55 μm – width of wool fibre{{cite web|url=http://www.istag.ch/fibres/applications.html|title=Fibreshape applications|publisher=IST - Innovative Sintering Technologies Ltd.|access-date=4 December 2008|quote=Histogram of Fiber Thickness [micrometre]}}
• 17 to 181 μm – diameter of human hairThe diameter of human hair ranges from 17 to 181 μm. {{cite web

| url=https://hypertextbook.com/facts/1999/BrianLey.shtml

| title=Diameter of a human hair

| first=Brian

| last=Ley

| year=1999

| website=The Physics Factbook

| editor-last=Elert

| editor-first=Glenn

| accessdate=2018-12-08}}

• 70 to 180 μm – thickness of paper

{{For|more examples of things measuring 10 to 100 micrometres|Orders of magnitude (length)#10 micrometres}}

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.[http://www.bipm.org/en/committees/cg/CGPM/13-1967/resolution-7/ BIPM - Resolution 7 of the 13th CGPM 1967/68)], "Abrogation of earlier decisions (micron, new candle.)" 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.

{{Anchor|Continuing_informal_usage_of_micron}} In American 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 ({{IPAc-en|m|aɪ|ˈ|k|r|ɒ|m|ɪ|t|ər}} {{respell|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 ({{IPAc-en|ˈ|m|aɪ|k|r|oʊ|m|iː|t|ər}} {{respell|MY|kroh|meet|ər}}).{{Original research inline|date=January 2025}}

The plural of micron is normally microns, though micra was occasionally used before 1950.{{cite book|url=https://books.google.com/books?id=92FOAAAAYAAJ&q=plural+of+micron+microns+or+micra&pg=PA80|title=Proceedings of the Royal Society of Queensland|publisher=H. Pole & Co.|year=1907|series=Part I|volume=XIX|via=Google Books}}{{cite book|url=https://books.google.com/books?id=lb3RAAAAMAAJ&q=plural+of+micron+microns+or+micra&pg=RA1-PA77|title=The Observer|last1=Bigalow|first1=Edward Fuller|last2=Agassiz Association|year=1905|volume=7–8|via=Google Books}}[https://books.google.com/ngrams/graph?content=10+micra%2F10+microns&year_start=1885&year_end=2000&corpus=15&smoothing=3&share=&direct_url=t1%3B%2C%2810%20micra%20/%2010%20microns%29%3B%2Cc0 10 micra/10 microns] (Start at 1885; before that, the word "micron", singular or plural, was rare)

{{See also|Micro-#Symbol encoding in character sets}}

The official symbol for the SI prefix micro- is a Greek lowercase mu.{{Cite web|url=https://www.bipm.org/en/measurement-units/prefixes.html|title=Prefixes of the International System of Units|publisher=International Bureau of Weights and Measures|access-date=9 May 2016|archive-date=23 May 2018|archive-url=https://web.archive.org/web/20180523190122/https://www.bipm.org/en/measurement-units/prefixes.html|url-status=dead}} Unicode has inherited {{unichar|00B5|MICRO SIGN}} from ISO/IEC 8859-1, distinct from the code point {{unichar|03BC|GREEK SMALL LETTER MU}}. According to the Unicode Consortium, the Greek letter character is preferred,{{Cite web|url=https://unicode.org/reports/tr25/|title=Unicode Technical Report #25|last1=Beeton|first1=Barbara|last2=Freytag|first2=Asmus|date=30 May 2017|website=Unicode Technical Reports|publisher=Unicode Consortium|page=11|last3=Sargent|first3=Murray III}} but implementations must recognize the micro sign as well for compatibility with legacy character sets. Most fonts use the same glyph for the two characters.

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 {{font|u|font=courier}}. For example, "15 μm" would appear as "{{font|1=15_{{{resize|130%|/}}}um|font=courier}}". This gave rise in early word processing to substituting just the letter {{font|u|font=roman}} for the symbol if the Greek letter μ was not available, as in "{{font|15 um|font=roman}}".{{cite book |title=The American Directory of Writer's Guidelines: A Compilation of Information for Freelancers from More Than 1,300 Magazine Editors and Book Publishers |editor=John C. Mutchler |page=47 |publisher=Quill Driver Books |year=1999 |isbn=978-1-884956-08-9 |url=https://books.google.com/books?id=94MYAAAAIAAJ&q=%22If+you+can-not+access+the+Greek+letter%22+%22use+the+Roman+lower-case+letter+u%22 |edition=2}}

The Unicode CJK Compatibility block contains square forms of some Japanese katakana measure and currency units.

{{Unichar|3348}} corresponds to {{lang|ja|ミクロン}} {{Transliteration|ja|mikuron}}.

• Metric prefix
• Metric system
• Orders of magnitude (length)
• Wool measurement

{{Reflist}}

• {{Wiktionary-inline|micrometre}}

{{SI units of length}}

Category:Metre

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