Micro (Greek letter μ, mu, non-italic) is a unit prefix in the metric system denoting a factor of 10−6 (one millionth). It comes from the Greek word μικρός (mikrós), meaning "small".
It is the only SI prefix which uses a character not from the Latin alphabet. In Unicode, the symbol is represented by U+03BC μ GREEK SMALL LETTER MU or the legacy symbol U+00B5 µ MICRO SIGN. The prefix "mc" is commonly used in healthcare or when the character "μ" is not available; for example, "mcg" commonly denotes a microgram. The letter "u" is sometimes used instead of "μ" when non-Latin characters are not available.
Examples
- Typical bacteria are 1 to 10 micrometer (1–10 μm) in diameter.
- Eukaryotic cells are typically 10 to 100 micrometers in diameter.
| Prefix | Base 10 | Decimal | Adoption | |
|---|---|---|---|---|
| Name | Symbol | |||
| quetta | Q | 1030 | 1000000000000000000000000000000 | 2022 |
| ronna | R | 1027 | 1000000000000000000000000000 | |
| yotta | Y | 1024 | 1000000000000000000000000 | 1991 |
| zetta | Z | 1021 | 1000000000000000000000 | |
| exa | E | 1018 | 1000000000000000000 | 1975 |
| peta | P | 1015 | 1000000000000000 | |
| tera | T | 1012 | 1000000000000 | 1960 |
| giga | G | 109 | 1000000000 | |
| mega | M | 106 | 1000000 | 1873 |
| kilo | k | 103 | 1000 | 1795 |
| hecto | h | 102 | 100 | |
| deca | da | 101 | 10 | |
| — | — | 100 | 1 | — |
| deci | d | 10−1 | 0.1 | 1795 |
| centi | c | 10−2 | 0.01 | |
| milli | m | 10−3 | 0.001 | |
| micro | μ | 10−6 | 0.000001 | 1873 |
| nano | n | 10−9 | 0.000000001 | 1960 |
| pico | p | 10−12 | 0.000000000001 | |
| femto | f | 10−15 | 0.000000000000001 | 1964 |
| atto | a | 10−18 | 0.000000000000000001 | |
| zepto | z | 10−21 | 0.000000000000000000001 | 1991 |
| yocto | y | 10−24 | 0.000000000000000000000001 | |
| ronto | r | 10−27 | 0.000000000000000000000000001 | 2022 |
| quecto | q | 10−30 | 0.000000000000000000000000000001 | |
| ||||
Symbol encoding in character sets
The official symbol for the SI prefix micro is a Greek lowercase mu (μ). For reasons stemming from its design, Unicode has two different character codes for the letter, with slightly different appearance in some fonts, although most fonts use the same glyph. U+00B5 µ MICRO SIGN (Alt+0181) is in the "Latin-1 Supplement" range identical to ISO/IEC 8859-1 (since 1987), residing at this code point also in DEC MCS (since 1983) and ECMA-94 (since 1985). U+03BC μ GREEK SMALL LETTER MU (Alt+956) is in the Greek range. 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. This distinction also occurs in some legacy code pages, notably Windows-1253.
In circumstances in which only the Latin alphabet is available, ISO 2955 (since 1974, withdrawn 2001), DIN 66030 (since 1980) and BS 6430 (since 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, or in the common abbreviation UC for microcontroller (μC). Similarly, capacitor values according to the RKM code defined in IEC 60062 (since 1952) can be written as 4u7 (or 4U7) instead of 4μ7 if the Greek letter μ is not available.
The CJK Compatibility block contains square forms of some Japanese katakana measure and currency units. U+3343 ㍃ SQUARE MAIKURO corresponds to マイクロ maikuro.
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. The two alternatives are to abbreviate as "mcg" or to write out "microgram" in full (see also List of abbreviations used in medical prescriptions). The alternative abbreviation may be ambiguous in rare circumstances in that mcg could also be read as a micrigram, i.e. 10−14 g; however the prefix micri is not standard, nor widely known, and is considered obsolete. 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), and in physical sciences research, "μg" remains the sole official abbreviation.
In medical data exchange according to the Health Level 7 (HL7) standard, the μ can be replaced by u as well.
See also
- Microgram
- Microscope
- Microsecond
- Microwave
- Square micrometre
- List of commonly used taxonomic affixes
References
- 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 2021-06-04, retrieved 2021-12-16
- "MICR," Merriam-Webster.com Dictionary, https://www.merriam-webster.com/dictionary/MICR. Accessed 10/13/2024.
- "ISMP List of Error-Prone Abbreviations, Symbols, and Dose Designations: Abbreviations for Doses/Measurement Units". Recommendations. Institute for Safe Medication Practices (ISMP). 2021-02-05. Archived from the original on 2022-12-24. Retrieved 2022-12-24.
Error-Prone Abbreviations, Symbols, and Dose Designations: μg […] Intended Meaning: Microgram […] Misinterpretation: Mistaken as mg […] Best Practice: Use mcg […]
- Biology by Campbell & Reece, tenth edition. Ch. 6 "A Tour of the Cell". p. 98.
- "On the extension of the range of SI prefixes". 2022-11-18. Retrieved 2023-02-05.
- "Metric (SI) Prefixes". NIST.
- Prefixes of the International System of Units, International Bureau of Weights and Measures (page visited on 9 May 2016).
- (Unicode 1.0, 1991)
- Unicode Technical Report #25
- ISO 2955-1974: Information processing - Representations of SI and other units for use in systems with limited character sets (1st ed.). 1974.
- "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. [1]
- DIN 66030: Darstellungen von Einheitennamen in Systemen mit beschränktem Schriftzeichenvorrat (in German) (1st ed.). 1980.
- "Neue Normen für die Informationsverarbeitung". Computerwoche (in German). 1981-01-09. Archived from the original on 2016-12-14. Retrieved 2016-12-14.
- Burtis, Carl A.; Ashwood, Edward R.; Bruns, David E. (2012), Tietz Textbook of Clinical Chemistry and Molecular Diagnostics (5th ed.), Elsevier Health Sciences, ISBN 978-1455759422.
- "Commonly Used UCUM Codes for Healthcare Units". HL7 Deutschland e.V. 2015-11-21. Archived from the original on 2022-10-06. Retrieved 2022-12-24.
Look up micro in Wiktionary the free dictionary Micro Greek letter m mu non italic is a unit prefix in the metric system denoting a factor of 10 6 one millionth It comes from the Greek word mikros mikros meaning small It is the only SI prefix which uses a character not from the Latin alphabet In Unicode the symbol is represented by U 03BC m GREEK SMALL LETTER MU or the legacy symbol U 00B5 µ MICRO SIGN The prefix mc is commonly used in healthcare or when the character m is not available for example mcg commonly denotes a microgram The letter u is sometimes used instead of m when non Latin characters are not available ExamplesTypical bacteria are 1 to 10 micrometer 1 10 mm in diameter Eukaryotic cells are typically 10 to 100 micrometers in diameter SI prefixesvte Prefix Base 10 Decimal AdoptionName Symbolquetta Q 1030 1000 000 000 000 000 000 000 000 000 000 2022ronna R 1027 1000 000 000 000 000 000 000 000 000yotta Y 1024 1000 000 000 000 000 000 000 000 1991zetta Z 1021 1000 000 000 000 000 000 000exa E 1018 1000 000 000 000 000 000 1975peta P 1015 1000 000 000 000 000tera T 1012 1000 000 000 000 1960giga G 109 1000 000 000mega M 106 1000 000 1873kilo k 103 1000 1795hecto h 102 100deca da 101 10 100 1 deci d 10 1 0 1 1795centi c 10 2 0 01milli m 10 3 0 001micro m 10 6 0 000001 1873nano n 10 9 0 000000 001 1960pico p 10 12 0 000000 000 001femto f 10 15 0 000000 000 000 001 1964atto a 10 18 0 000000 000 000 000 001zepto z 10 21 0 000000 000 000 000 000 001 1991yocto y 10 24 0 000000 000 000 000 000 000 001ronto r 10 27 0 000000 000 000 000 000 000 000 001 2022quecto q 10 30 0 000000 000 000 000 000 000 000 000 001NotesPrefixes adopted before 1960 already existed before SI The introduction of the CGS system was in 1873 Symbol encoding in character setsThe official symbol for the SI prefix micro is a Greek lowercase mu m For reasons stemming from its design Unicode has two different character codes for the letter with slightly different appearance in some fonts although most fonts use the same glyph U 00B5 µ MICRO SIGN Alt 0181 is in the Latin 1 Supplement range identical to ISO IEC 8859 1 since 1987 residing at this code point also in DEC MCS since 1983 and ECMA 94 since 1985 U 03BC m GREEK SMALL LETTER MU Alt 956 is in the Greek range 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 This distinction also occurs in some legacy code pages notably Windows 1253 In circumstances in which only the Latin alphabet is available ISO 2955 since 1974 withdrawn 2001 DIN 66030 since 1980 and BS 6430 since 1983 allow the prefix m to be substituted by the letter a href wiki U title U u a or even a href wiki U title U U a if lowercase letters are not available as for example in um for mm or uF for mF or in the common abbreviation UC for microcontroller mC Similarly capacitor values according to the RKM code defined in IEC 60062 since 1952 can be written as 4u7 or 4U7 instead of 4m7 if the Greek letter m is not available The CJK Compatibility block contains square forms of some Japanese katakana measure and currency units U 3343 SQUARE MAIKURO corresponds to マイクロ maikuro Other abbreviating conventionsIn some health care institutions house rules deprecate the standard symbol for microgram mg in prescribing or chart recording because of the risk of giving an incorrect dose because of the misreading of poor handwriting The two alternatives are to abbreviate as mcg or to write out microgram in full see also List of abbreviations used in medical prescriptions The alternative abbreviation may be ambiguous in rare circumstances in that mcg could also be read as a micrigram i e 10 14 g however the prefix micri is not standard nor widely known and is considered obsolete 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 and in physical sciences research mg remains the sole official abbreviation In medical data exchange according to the Health Level 7 HL7 standard the m can be replaced by u as well See alsoMicrogram Microscope Microsecond Microwave Square micrometre List of commonly used taxonomic affixesReferencesInternational 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 2021 06 04 retrieved 2021 12 16 MICR Merriam Webster com Dictionary https www merriam webster com dictionary MICR Accessed 10 13 2024 ISMP List of Error Prone Abbreviations Symbols and Dose Designations Abbreviations for Doses Measurement Units Recommendations Institute for Safe Medication Practices ISMP 2021 02 05 Archived from the original on 2022 12 24 Retrieved 2022 12 24 Error Prone Abbreviations Symbols and Dose Designations mg Intended Meaning Microgram Misinterpretation Mistaken as mg Best Practice Use mcg Biology by Campbell amp Reece tenth edition Ch 6 A Tour of the Cell p 98 On the extension of the range of SI prefixes 2022 11 18 Retrieved 2023 02 05 Metric SI Prefixes NIST Prefixes of the International System of Units International Bureau of Weights and Measures page visited on 9 May 2016 Unicode 1 0 1991 Unicode Technical Report 25 ISO 2955 1974 Information processing Representations of SI and other units for use in systems with limited character sets 1st ed 1974 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 1 DIN 66030 Darstellungen von Einheitennamen in Systemen mit beschranktem Schriftzeichenvorrat in German 1st ed 1980 Neue Normen fur die Informationsverarbeitung Computerwoche in German 1981 01 09 Archived from the original on 2016 12 14 Retrieved 2016 12 14 Burtis Carl A Ashwood Edward R Bruns David E 2012 Tietz Textbook of Clinical Chemistry and Molecular Diagnostics 5th ed Elsevier Health Sciences ISBN 978 1455759422 Commonly Used UCUM Codes for Healthcare Units HL7 Deutschland e V 2015 11 21 Archived from the original on 2022 10 06 Retrieved 2022 12 24 Portal Physics
