Micro-

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Comparison between the micro symbol and the Greek letter mu in Linux Libertine Micro symbol vs Greek mu in Linux Libertine.svg
Comparison between the micro symbol and the Greek letter mu in Linux Libertine

Micro- (Greek letter μ or legacy micro symbol µ) is a unit prefix in the metric system denoting a factor of 10−6 (one millionth). [1] Confirmed in 1960, the prefix comes from the Greek μικρός (mikrós), meaning "small".

A metric prefix is a unit prefix that precedes a basic unit of measure to indicate a multiple or fraction of the unit. While all metric prefixes in common use today are decadic, historically there have been a number of binary metric prefixes as well. Each prefix has a unique symbol that is prepended to the 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.

Metric system Decimal system of units of measurement

The metric system is an internationally recognised decimalised system of measurement. It is in widespread use, and where it is adopted, it is the only or most common system of weights and measures. It is now known as the International System of Units (SI). It is used to measure everyday things such as the mass of a sack of flour, the height of a person, the speed of a car, and the volume of fuel in its tank. It is also used in science, industry and trade.

One millionth is equal to 0.000 001, or 1 x 10−6 in scientific notation. It is the reciprocal of a million, and can be also written as 1/1 000 000. Units using this fraction can be indicated using the prefix "micro-" from Greek, meaning "small". Numbers of this quantity are expressed in terms of µ.

Contents

The symbol for the prefix comes from the Greek letter μ (mu). It is the only SI prefix which uses a character not from the Latin alphabet. "mc" is commonly used as a prefix when the character "μ" is not available; for example, "mcg" commonly denotes a microgram. Also the letter u instead of μ is allowed by one of the ISO documents. [2]

Mu or my is the 12th letter of the Greek alphabet. 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.

International System of Units a system of units of measurement for base and derived physical quantities

The International System of Units is the modern form of the metric system, and is the most widely used system of measurement. It comprises a coherent system of units of measurement built on seven base units, which are the second, metre, kilogram, ampere, kelvin, mole, candela, and a set of twenty prefixes to the unit names and unit symbols that may be used when specifying multiples and fractions of the units. The system also specifies names for 22 derived units, such as lumen and watt, for other common physical quantities.

Latin alphabet Alphabet used to write the Latin language

The Latin or Roman alphabet is the writing system originally used by the ancient Romans to write the Latin language.

Examples:

Bacteria A domain of prokaryotes – single celled organisms without a nucleus

Bacteria are a type of biological cell. They constitute a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth, and are present in most of its habitats. Bacteria inhabit soil, water, acidic hot springs, radioactive waste, and the deep portions of Earth's crust. Bacteria also live in symbiotic and parasitic relationships with plants and animals. Most bacteria have not been characterised, and only about 27 percent of the bacterial phyla have species that can be grown in the laboratory . The study of bacteria is known as bacteriology, a branch of microbiology.

Eukaryote taxonomic group whose members have complex structures enclosed within membranes

Eukaryotes are organisms whose cells have a nucleus enclosed within membranes, unlike prokaryotes, which have no membrane-bound organelles. Eukaryotes belong to the domain Eukaryota or Eukarya. Their name comes from the Greek εὖ and κάρυον. Eukaryotic cells also contain other membrane-bound organelles such as mitochondria and the Golgi apparatus, and in addition, some cells of plants and algae contain chloroplasts. Unlike unicellular archaea and bacteria, eukaryotes may also be multicellular and include organisms consisting of many cell types forming different kinds of tissue. Animals and plants are the most familiar eukaryotes.

PrefixBase 1000Base 10 Decimal English wordAdoption [nb 1]
NameSymbol Short scale Long scale
yotta Y 10008  1024 1000000000000000000000000 septillion quadrillion1991
zetta Z 10007  1021 1000000000000000000000 sextillion trilliard1991
exa E 10006  1018 1000000000000000000 quintillion trillion1975
peta P 10005  1015 1000000000000000 quadrillion billiard1975
tera T 10004  1012 1000000000000 trillion billion1960
giga G 10003  109 1000000000 billion milliard1960
mega M 10002  106 1000000 million1873
kilo k 10001  103 1000 thousand1795
hecto h 10002/3  102 100 hundred1795
deca da 10001/3  101 10 ten1795
 10000  100 1 one
deci d 1000−1/3  10−1 0.1 tenth1795
centi c 1000−2/3   10−2 0.01 hundredth1795
milli m 1000−1  10−3 0.001 thousandth1795
micro μ 1000−2  10−6 0.000001 millionth1873
nano n 1000−3  10−9 0.000000001 billionth milliardth1960
pico p 1000−4  10−12 0.000000000001 trillionth billionth1960
femto f 1000−5  10−15 0.000000000000001 quadrillionth billiardth1964
atto a 1000−6  10−18 0.000000000000000001 quintillionth trillionth1964
zepto z 1000−7  10−21 0.000000000000000000001 sextillionth trilliardth1991
yocto y 1000−8  10−24  0.000000000000000000000001 septillionth quadrillionth1991
  1. Prefixes adopted before 1960 already existed before SI. 1873 was the introduction of the CGS system.

Symbol encoding in character sets

The official symbol for the SI prefix micro- is a Greek lowercase mu (μ). [4] For reasons stemming from its design, there are two different characters in Unicode, which appear slightly different in some fonts, although most fonts use the same glyph. The micro sign (µ) is encoded in the "Latin-1 Supplement" range identical to ISO/IEC 8859-1 (since 1987), at U+00B5 (Alt+0181), [5] residing at this code point also in DEC MCS (since 1983) and ECMA-94 (since 1985). The Greek letter (μ) is encoded in the Greek range at U+03BC (Alt+956). According to The Unicode Consortium, the Greek letter character is preferred, [6] but implementations must recognize the micro sign as well.

Unicode Character encoding standard

Unicode is a computing industry standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard is maintained by the Unicode Consortium, and as of May 2019 the most recent version, Unicode 12.1, contains a repertoire of 137,994 characters covering 150 modern and historic scripts, as well as multiple symbol sets and emoji. The character repertoire of the Unicode Standard is synchronized with ISO/IEC 10646, and both are code-for-code identical.

ISO/IEC 8859-1 character encoding

ISO/IEC 8859-1:1998, Information technology — 8-bit single-byte coded graphic character sets — Part 1: Latin alphabet No. 1, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. ISO 8859-1 encodes what it refers to as "Latin alphabet no. 1", consisting of 191 characters from the Latin script. This character-encoding scheme is used throughout the Americas, Western Europe, Oceania, and much of Africa. It is also commonly used in most standard romanizations of East-Asian languages. It is the basis for most popular 8-bit character sets and the first block of characters in Unicode.

In circumstances in which only the Latin alphabet is available, ISO 2955 (1974, [7] 1983 [8] ), DIN 66030 (Vornorm 1973; [9] 1980, [10] [11] 2002 [12] ) and BS 6430 (1983) allow the prefix μ to be substituted by the letter u (or even U , if lowercase letters are not available), as, for example, in um for μm, or uF for μF. Similar, capacitor values according to the RKM code defined in IEC 60062 (IEC 62) (since 1952), EN 60062, DIN 40825 (1973), BS 1852 (1974), IS 8186 (1976) etc. can be written as 4u7 (or 4U7) instead of 4μ7 if the Greek letter μ is not available.

The RKM code, also referred to as "letter and digit code for resistance and capacitance values and tolerances" or "R notation", is a notation to specify resistor and capacitor values defined in the international standard IEC 60062 since 1952. It is also adopted by various other standards including DIN 40825 (1973), BS 1852 (1974), IS 8186 (1976) and EN 60062 (1993). The significantly updated IEC 60062:2016 comprises the most recent release of the standard.

Other abbreviating conventions

In some health care institutions, house rules deprecate the standard symbol for microgram, "μg", in prescribing or chart recording, because of the risk of giving an incorrect dose because of the misreading of poor handwriting. [13] The two alternatives are to abbreviate as "mcg" [13] or to write out "microgram" in full (see also List of abbreviations used in medical prescriptions). But this deprecation, focused on avoiding incorrect dosing in contexts where handwriting is often present, does not extend to all health-care contexts and institutions (for example, some clinical laboratories' reports adhere to it, whereas others do not [13] ), and in physical sciences academia, "μg" remains the sole official abbreviation.

Health care Prevention of disease and promotion of wellbeing

Health care or healthcare is the maintenance or improvement of health via the prevention, diagnosis, and treatment of disease, illness, injury, and other physical and mental impairments in people. Health care is delivered by health professionals in allied health fields. Physicians and physician associates are a part of these health professionals. Dentistry, midwifery, nursing, medicine, optometry, audiology, pharmacy, psychology, occupational therapy, physical therapy and other health professions are all part of health care. It includes work done in providing primary care, secondary care, and tertiary care, as well as in public health.

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 when communicating medical information is mcg. In μg the prefix symbol for micro- is the Greek letter μ (Mu).

In medical data exchange according to the Health Level 7 (HL7) standard, the μ can be replaced by u as well. [14]

See also

Related Research Articles

Micrometre one millionth of a metre

The micrometre or micrometer, also commonly known by the previous name micron, is an SI derived unit of length equalling 1×10−6 metre ; that is, one millionth of a metre.

In computer and machine-based telecommunications terminology, a character is a unit of information that roughly corresponds to a grapheme, grapheme-like unit, or symbol, such as in an alphabet or syllabary in the written form of a natural language.

ISO/IEC 8859-7:2003, Information technology — 8-bit single-byte coded graphic character sets — Part 7: Latin/Greek alphabet, is part of the ISO/IEC 8859 series of ASCII-based standard character encodings, first edition published in 1987. It is informally referred to as Latin/Greek. It was designed to cover the modern Greek language. The original 1987 version of the standard had the same character assignments as the Greek national standard ELOT 928, published in 1986. The table in this article shows the updated 2003 version which adds three characters. Microsoft has assigned code page 28597 a.k.a. Windows-28597 to ISO-8859-7 in Windows. IBM has assigned code page 813 to ISO 8859-7.

The Greek alphabet has been used to write the Greek language since the late ninth or early eighth century BC. It is derived from the earlier Phoenician alphabet, and was the first alphabetic script to have distinct letters for vowels as well as consonants. In Archaic and early Classical times, the Greek alphabet existed in many different local variants, but, by the end of the fourth century BC, the Eucleidean alphabet, with twenty-four letters, ordered from alpha to omega, had become standard and it is this version that is still used to write Greek today. These twenty-four letters are: Α α, Β β, Γ γ, Δ δ, Ε ε, Ζ ζ, Η η, Θ θ, Ι ι, Κ κ, Λ λ, Μ μ, Ν ν, Ξ ξ, Ο ο, Π π, Ρ ρ, Σ σ/ς, Τ τ, Υ υ, Φ φ, Χ χ, Ψ ψ, and Ω ω.

Thai Industrial Standard 620-2533, commonly referred to as TIS-620, is the most common character set and character encoding for the Thai language. The standard is published by the Thai Industrial Standards Institute (TISI), an organ of the Ministry of Industry under the Royal Thai Government, and is the sole official standard for encoding Thai in Thailand. The descriptive name of the standard is "Standard for Thai Character Codes for Computers". "2533" refers to year 2533 of the Buddhist Era (1990), the year the present version of the standard was published; a previous revision, TIS 620-2529 (1986), is now obsolete.

Kra (letter) letter of the Latin alphabet

Kra is a glyph formerly used to write the Kalaallisut language of Greenland and is now only found in Nunatsiavummiutut, a distinct Inuktitut dialect. It is visually similar to a Latin small capital letter K and the Greek letter kappa κ.

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Unicode has a certain amount of duplication of characters. These are pairs of single Unicode code points that are canonically equivalent. The reason for this are compatibility issues with legacy systems.

ISO 80000 or IEC 80000 is an international standard promulgated jointly by the International Organization for Standardization (ISO) and the International Electrotechnical Commission (IEC).

Unicode input

Unicode input is the insertion of a specific Unicode character on a computer by a user; it is a common way to input characters not directly supported by a physical keyboard. Unicode characters can be produced either by selecting them from a display or by typing a certain sequence of keys on a physical keyboard. In addition, a character produced by one of these methods in one web page or document can be copied into another. Unicode is similar to ASCII but provides many more options and encodes many more signs.

The ISO basic Latin alphabet is a Latin-script alphabet and consists of two sets of 26 letters, codified in various national and international standards and used widely in international communication. They are the same letters that comprise the English alphabet.

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References

  1. International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), ISBN   92-822-2213-6, archived (PDF) from the original on 2017-08-14
  2. ISO 2955, table 2.
  3. Biology by Campbell & Reece, tenth edition. Ch. 6 "A Tour of the Cell". p. 98.
  4. Prefixes of the International System of Units, International Bureau of Weights and Measures (page visited on 9 May 2016).
  5. (Unicode 1.0, 1991)
  6. Unicode Technical Report #25
  7. ISO 2955-1974: lnformation processing - Representations of SI and other units for use in systems with limited character sets (1st ed.). 1974.
  8. "Table 2". ISO 2955-1983: lnformation processing - Representations of SI and other units for use in systems with limited character sets (PDF) (2nd ed.). 1983-05-15. Retrieved 2016-12-14.
  9. Vornorm DIN 66030[Preliminary standard DIN 66030] (in German). January 1973.
  10. DIN 66030: Darstellungen von Einheitennamen in Systemen mit beschränktem Schriftzeichenvorrat (in German) (1st ed.). 1980.
  11. "Neue Normen für die Informationsverarbeitung". Computerwoche (in German). 1981-01-09. Archived from the original on 2016-12-14. Retrieved 2016-12-14.
  12. DIN 66030:2002-05 - Informationstechnik - Darstellung von Einheitennamen in Systemen mit beschränktem Schriftzeichenvorrat [Information technology - Representation of SI and other units in systems with limited character sets] (in German). Beuth Verlag  [ de ]. May 2002. Retrieved 2016-12-14.
  13. 1 2 3 Burtis, Carl A.; Ashwood, Edward R.; Bruns, David E. (2012), Tietz Textbook of Clinical Chemistry and Molecular Diagnostics (5th ed.).
  14. "Commonly Used UCUM Codes for Healthcare Units". HL7 Deutschland e.V. Retrieved 2015-11-21.