micrometre | |
---|---|

General information | |

Unit system | SI |

Unit of | length |

Symbol | μm |

Conversions | |

1 μm in ... | ... is equal to ... |

SI base units | 10^{−6} m |

Natural units | 1.8897×10^{4} a_{0} |

imperial/US units | 3.9370×10^{−5} in |

The **micrometre** (international spelling as used by the International Bureau of Weights and Measures;^{ [1] } SI symbol: **μm**) or **micrometer** (American spelling), also commonly known as a **micron**, is a unit of length in the International System of Units (SI) equalling 1×10^{−6} metre (SI standard prefix "micro-" = 10^{−6}); that is, one millionth of a metre (or one thousandth of a millimetre, 0.001 mm, or about 0.00004 inch ).^{ [1] }

The nearest smaller common SI unit is the nanometre, equivalent to one one-thousandth of a micrometre, or one billionth of a metre (0.000000001 m).

The micrometre is a common unit of measurement for wavelengths of infrared radiation as well as sizes of biological cells and bacteria,^{ [1] } and for grading wool by the diameter of the fibres.^{ [2] } The width of a single human hair ranges from approximately 20 to 200 μm. The longest human chromosome, chromosome 1, is approximately 10 μm in length.

Between 1 μm and 10 μm:

- 1–10 μm – length of a typical bacterium
- 3–8 μm – width of strand of spider web silk
^{ [3] } - 5 μm – length of a typical human spermatozoon's head
^{ [4] } - 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
^{ [5] } - 17 to 181 μm – diameter of human hair
^{ [6] } - 70 to 180 μm – thickness of paper

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.^{ [7] } 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.

Additionally, 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 ( /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 ( /ˈmaɪkroʊˌmiːtər/ *MY-kroh-meet-ər*).

The plural of *micron* is normally *microns*, though *micra* was occasionally used before 1950.^{ [8] }^{ [9] }^{ [10] }

The official symbol for the SI prefix *micro-* is a Greek lowercase mu.^{ [11] } In Unicode, there is also a micro sign with the code point U+00B5 (µ), distinct from the code point U+03BC (μ) of the Greek letter lowercase mu. According to the Unicode Consortium, the Greek letter character is preferred,^{ [12] } but implementations must recognize the micro sign as well. Most fonts use the same glyph for the two characters.

- 1 2 3 "micrometre".
*Encyclopædia Britannica Online*. Retrieved 18 May 2014. - ↑ "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*) - ↑ Smith, D.J.; Gaffney, E.A.; Blake, J.R.; Kirkman-Brown, J.C. (25 February 2009). "Human sperm accumulation near surfaces: a simulation study" (PDF).
*Journal of Fluid Mechanics*. Cambridge University Press.**621**: 295. Bibcode:2009JFM...621..289S. doi:10.1017/S0022112008004953. S2CID 3942426. Archived from the original (PDF) on 6 November 2013. - ↑ "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. - ↑ BIPM - Resolution 7 of the 13th CGPM 1967/68), "Abrogation of earlier decisions (micron, new candle.)"
- ↑
*Proceedings of the Royal Society of Queensland*. Part I. Vol. XIX. H. Pole & Co. 1907 – via Google Books. - ↑ Bigalow, Edward Fuller; Agassiz Association (1905).
*The Observer*. Vol. 7–8 – via Google Books. - ↑ 10 micra/10 microns (Start at 1885; before that, the word "micron", singular or plural, was rare)
- ↑ "Prefixes of the International System of Units". International Bureau of Weights and Measures. Archived from the original on 23 May 2018. Retrieved 9 May 2016.
- ↑ Beeton, Barbara; Freytag, Asmus; Sargent, Murray III (30 May 2017). "Unicode Technical Report #25".
*Unicode Technical Reports*. Unicode Consortium. p. 11.

- The dictionary definition of
*micrometre*at Wiktionary

A **centimetre** or **centimeter** is a unit of length in the International System of Units (SI), equal to one hundredth of a metre, *centi* being the SI prefix for a factor of 1/100. The centimetre was the base unit of length in the now deprecated centimetre–gram–second (CGS) system of units.

In geometry, a **diameter** of a circle is any straight line segment that passes through the center of the circle and whose endpoints lie on the circle. It can also be defined as the longest chord of the circle. Both definitions are also valid for the diameter of a sphere.

The **litre** or **liter** is a metric unit of volume. It is equal to 1 cubic decimetre (dm^{3}), 1000 cubic centimetres (cm^{3}) or 0.001 cubic metre (m^{3}). A cubic decimetre occupies a volume of 10 cm × 10 cm × 10 cm and is thus equal to one-thousandth of a cubic metre.

A **micron** is a non-SI name for micrometre (μm).

The **nanometre** or **nanometer** is a unit of length in the International System of Units (SI), equal to one billionth of a metre and to 1000 picometres. One nanometre can be expressed in scientific notation as 1×10^{−9} m, and as 1/1000000000 metres.

A **metric prefix** is a unit prefix that precedes a basic unit of measure to indicate a multiple or submultiple of the unit. All metric prefixes used today are decadic. Each prefix has a unique symbol that is prepended to any unit symbol. The prefix *kilo-*, for example, may be added to *gram* to indicate *multiplication* by one thousand: one kilogram is equal to one thousand grams. The prefix *milli-*, likewise, may be added to *metre* to indicate *division* by one thousand; one millimetre is equal to one thousandth of a metre.

The **picometre** or **picometer** is a unit of length in the International System of Units (SI), equal to 1×10^{−12} m, or one trillionth (1/1000000000000) of a metre, which is the SI base unit of length.

The **millimetre** or **millimeter** is a unit of length in the International System of Units (SI), equal to one thousandth of a metre, which is the SI base unit of length. Therefore, there are one thousand millimetres in a metre. There are ten millimetres in a centimetre.

The **square metre** or **square meter** is the unit of area in the International System of Units (SI) with symbol **m ^{2}**. It is the area of a square with sides one metre in length.

**Mu** is the 12th letter of the Greek alphabet, representing the voiced bilabial nasal IPA: [m]. In the system of Greek numerals it has a value of 40. Mu was derived from the Egyptian hieroglyphic symbol for water, which had been simplified by the Phoenicians and named after their word for water, to become 𐤌 (mem). Letters that derive from mu include the Roman M and the Cyrillic М.

* Micro* is a unit prefix in the metric system denoting a factor of 10

The following are examples of orders of magnitude for different lengths.

In the metric system, a **microgram** or **microgramme** is a unit of mass equal to one millionth of a gram. The unit symbol is **μg** according to the International System of Units; the recommended symbol in the United States and United Kingdom when communicating medical information is **mcg**. In μg the prefix symbol for micro- is the Greek letter μ (mu).

A **thousandth of an inch** is a derived unit of length in a system of units using inches. Equal to 1⁄1000 of an inch, a thousandth is commonly called a **thou** or particularly in North America a **mil**.

A **micron** (micrometre) is the measurement used to express the diameter of wool fibre. Fine wool fibers have a low micron value. Fibre diameter is the most important characteristic of wool in determining its value.

**Animal fibers** are natural fibers that consist largely of certain proteins. Examples include silk, hair/fur and feathers. The animal fibers used most commonly both in the manufacturing world as well as by the hand spinners are wool from domestic sheep and silk. Also very popular are alpaca fiber and mohair from Angora goats. Unusual fibers such as Angora wool from rabbits and Chiengora from dogs also exist, but are rarely used for mass production.

Textile fibers, threads, yarns and fabrics are measured in a multiplicity of units.

An **S number** on the label of wool suits or other tailored apparel, wool fabric, or yarn, indicates the fineness of the wool fiber used in the making of the apparel, as measured by its maximum diameter in micrometres. Fiber fineness is one of the factors determining the quality and performance of a wool product. In recent years it has also become an important marketing device used by many mills, garment makers, and retailers. The S number appears as a plural with an *s* or *'s* following the number, such as *100s* or *100's.*

The **cubic metre** or **cubic meter** is the unit of volume in the International System of Units (SI). Its symbol is **m ^{3}**. It is the volume of a cube with edges one metre in length. An alternative name, which allowed a different usage with metric prefixes, was the stère, still sometimes used for dry measure. Another alternative name, no longer widely used, was the kilolitre.

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