Micrometre

Examples

Between 1 μm and 10 μm:

• 1–10 μm – length of a typical bacterium
• 3–8 μm – width of strand of spider web silk
• 5 μm – length of a typical human spermatozoon's head
• 6–8 μm – diameter of a typical red blood cell
• 10 μm – size of fungal hyphae
• about 10 μm – size of a fog, mist, or cloud water droplet

Between 10 μm and 100 μm:

• about 10–12 μm – thickness of plastic wrap (cling wrap)
• 10 to 55 μm – width of wool fibre
• 17 to 181 μm – diameter of human hairThe diameter of human hair ranges from 17 to 181 μm. {{cite web | editor-last=Elert | editor-first=Glenn
• 70 to 180 μm – thickness of paper

SI standardization

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. 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.

Continuing_informal_usage_of_micron In American English, the use of micron may help to differentiate the unit from the micrometer, a measuring device, because the unit's name in American spelling is a homograph of the device's name. In spoken English, they are distinguished by pronunciation, as the name of the measuring device is stressed on the second syllable ( ), whereas the unit name places the stress on the first syllable ( ).

The plural of micron is normally microns, though micra was occasionally used before 1950.

Symbol

The official symbol for the SI prefix micro- is a Greek lowercase mu. Unicode has inherited from ISO/IEC 8859-1, distinct from the code point . According to the Unicode Consortium, the Greek letter character is preferred, 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 . For example, "15 μm" would appear as "". This gave rise in early word processing to substituting just the letter for the symbol if the Greek letter μ was not available, as in "".

The Unicode CJK Compatibility block contains square forms of some Japanese katakana measure and currency units. corresponds to ミクロン ja.

References

1. "micrometre".
2. "Wool Fibre". NSW Department of Education and Communities.
3. Ramel. "Spider Silk".
4. (25 February 2009). "Human sperm accumulation near surfaces: a simulation study". [[Cambridge University Press]].
5. "Red Blood Cell (RBC) Size Variation".
6. "Fibreshape applications". IST - Innovative Sintering Technologies Ltd..
7. [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.)"
8. (13 January 2010). "Writing with SI (Metric System) Units". NIST.
9. {{cite LPD. 3
10. (1907). "Proceedings of the Royal Society of Queensland". H. Pole & Co..
11. (1905). "The Observer".
12. "Prefixes of the International System of Units". [[International Bureau of Weights and Measures]].
13. (30 May 2017). "Unicode Technical Report #25". [[Unicode Consortium]].
14. (1999). "The American Directory of Writer's Guidelines: A Compilation of Information for Freelancers from More Than 1,300 Magazine Editors and Book Publishers". Quill Driver Books.