Unit prefix
A unit prefix is a specifier or mnemonic that is prepended to
Metric prefixes
Prefix | Symbol | Factor | Power |
---|---|---|---|
tera | T | 1000000000000 | 1012 |
giga | G | 1000000000 | 109 |
mega | M | 1000000 | 106 |
kilo | k | 1000 | 103 |
hecto | h | 100 | 102 |
deca | da | 10 | 101 |
(none) | (none) | 1 | 100 |
deci | d | 0.1 | 10−1 |
centi | c | 0.01 | 10−2 |
milli | m | 0.001 | 10−3 |
micro | μ | 0.000001 | 10−6 |
nano | n | 0.000000001 | 10−9 |
pico | p | 0.000000000001 | 10−12 |
The prefixes of the
Although formerly in use, the SI disallows combining prefixes; the *microkilogram or *centimillimetre, for example, are not permitted. Prefixes corresponding to powers of one thousand are usually preferred, however, units such as the hectopascal, hectare, decibel, centimetre, and centilitre, are commonly used. The unit prefixes are always considered to be part of the unit, so that, e.g., in exponentiation, 1 km2 means one square kilometre, not one thousand square metres, and 1 cm3 means one cubic centimetre, not one hundredth of a cubic metre.
In general, prefixes are used with any metric unit, but may also be used with non-metric units. Some combinations, however, are more common than others. The choice of prefixes for a given unit has often arisen by convenience of use and historical developments. Unit prefixes that are much larger or smaller than encountered in practice are seldom used, albeit valid combinations. In most contexts only a few, the most common, combinations are established. For example, prefixes for multiples greater than one thousand are rarely applied to the gram or metre.
Some prefixes used in older versions of the metric system are no longer used. The prefixes
Binary prefixes
Prefix | Symbol | Power |
---|---|---|
yobi | Yi | 280 |
zebi | Zi | 270 |
exbi | Ei | 260 |
pebi | Pi | 250 |
tebi | Ti | 240 |
gibi | Gi | 230 |
mebi | Mi | 220 |
kibi | Ki | 210 |
A binary prefix indicates multiplication by a power of two. The tenth power of 2 (210) has the value 1024, which is close to 1000. This has prompted the use of the metric prefixes kilo, mega, and giga to also denote the powers of 1024 which is common in information technology with the unit of digital information, the byte.
Units of information are not covered in the International System of Units. Computer professionals have historically used the same spelling, pronunciation and symbols for the binary series in the description of computer memory, although the symbol for kilo is often capitalised. For example, in citations of main memory or RAM capacity, kilobyte, megabyte and gigabyte customarily mean 1024 (210), 1048576 (220) and 1073741824 (230) bytes respectively.
In the specifications of
To protect themselves, some sellers write out the full term as "1000000".With the aim of avoiding ambiguity the
Unofficial prefixes
Although some of the following unofficial prefixes appear repeated on the internet, no one is in actual use.[11]
A metric prefix myria (abbreviation "my"), for 10,000, was deprecated in 1960. Before the adoption of ronna and quetta for 1027 and 1030 and ronto and quecto for 10−27 and 10−30 in November 2022, many personal, and sometimes facetious, proposals for additional metric prefixes were formulated.[12][13] The prefix bronto, as used in the term "brontobyte", has been used to represent anything from 1015 to 1027 bytes, most often 1027.[14][15][16][17][18]
In 2010, an online petition sought to establish
The ascending prefixes peta (10005) and exa (10006) are based on the Greek-derived
Before the adoption of new prefixes in 2022, several personal proposals had been made for extending the series of prefixes, with ascending terms such as xenna, weka, vendeka (from Greek "ennea" (9), "deka" (10), "endeka" (11)) and descending terms such as xono, weco, vundo (from Latin "novem"/"nona" (9), "decem" (10), "undecim" (11)). Using Greek for ascending and Latin for descending would be consistent with established prefixes such as deca, hecto, kilo vs. deci, centi, milli.[26]
In 2001, a few unofficial prefixes appeared on the Internet: hepa (1021), ento (10−21), otta (1024), fito (10−24), nea (1027), syto (10−27), dea (1030), tredo (1030), una (1033) and revo (10−33). The Oxford professor
See also
Notes
- ^ "The names zepto and zetta suggest the digit seven [sept] (seventh power of 103) and the letter 'z' replaces the letter 's' to avoid the duplicate use of the letter 's' as a symbol. The names yocto and yotta are derived from octo, which suggests the number eight (eighth power of 103); the letter 'y' is added to avoid the use of the letter 'o' as a symbol because of the possible confusion with the digit zero." Resolution 4 of the 19th CGPM (1991)
References
- ^ "Four Resolutions". Bipm.org. Retrieved 2012-03-01.
- ^ 29th Congress of the United States, Session 1 (1866-05-13). "H.R. 596, An Act to authorise the use of the metric system of weights and measures". Archived from the original on 2013-01-14.
{{cite web}}
: CS1 maint: numeric names: authors list (link) - ^ a b Brewster, David (1830). The Edinburgh Encyclopædia. Vol. 12. Edinburgh, UK: William Blackwood, John Waugh, John Murray, Baldwin & Cradock, J. M. Richardson. p. 494. Retrieved 2015-10-09.
- ^ a b Brewster, David (1832). The Edinburgh Encyclopaedia. Vol. 12 (1st American ed.). Joseph and Edward Parker. Retrieved 2015-10-09.
- ^ "La Loi Du 18 Germinal An 3: Décision de tracer le mètre, unité fondamentale, sur une règle de platine. Nomenclature des " mesures républicaines ". Reprise de la triangulation" [The Law of 18 Germinal, Year 3: Decision to draw the fundamental unit metre on a platinum ruler. Nomenclature of "Republican measures". Resumption of the triangulation.]. L'Histoire Du Mètre [The history of the metre] (in French). histoire.du.metre.free.fr. Archived from the original on 2022-11-26. Retrieved 2015-10-12.
Art. 8. Dans les poids et mesures de capacité, chacune des mesures décimales de ces deux genres aura son double et sa moitié, afin de donner à la vente des divers objets toute la commodité que l'on peut désirer. Il y aura donc le double-litre et le demi-litre, le double-hectogramme et le demi-hectogramme, et ainsi des autres.
[Art. 8. In the weights and measures of capacity, each of the decimal measures of these two kinds will have its double and its half, in order to give to the sale of the various articles all the convenience that one can desire. There will therefore be the double-litre and the half-litre, the double-hectogram and the half-hectogram, and so on.] - ^ Dingler, Johann Gottfried (1823). Polytechnisches Journal (in German). Vol. 11. Stuttgart, Germany: J.W. Gotta'schen Buchhandlung. Retrieved 2015-10-09.
- ^ Shrivatav, P. N., ed. (1971). "Appendix B - XII Conversion Table". Gazetteer of India: Madhya Pradesh District Gazetteers - Indore. District Gazetteers Department, Madhya Pradesh, Bhopal. p. 785.
- ^ Reimer, Jeremy (2006-06-30). "Western Digital settles drive size lawsuit". Ars Technica LLC. Retrieved 2012-02-18.
- ^ Seagate lawsuit concludes, settlement announced, bit-tech.net
- ^ "International System of Units (SI): Prefixes for binary multiples". The NIST Reference on Constants, Units, and Uncertainty. National Institute of Science and Technology. Retrieved 2007-09-09.
- ^ "Large Numbers – Notes (page 3) at MROB". Archived from the original on 2022-12-21. Retrieved 2022-12-24.
- ^ Calvin (2021) [2020, 2000-11-05]. Michon, Gerard P. (ed.). "Current and Deprecated Prefixes". Archived from the original on 2022-12-21. Retrieved 2022-12-24.
- ^ Foley, John (2002-05-27). "Funny prefixes & dubious proposals (updated yearly)". Archived from the original on 2022-12-24. Retrieved 2022-12-24.
- ^ a b Michon, Gerard P. (2013-10-09). "Extreme Big Data: Beyond Zettabytes And Yottabytes". Forbes. Archived from the original on 2022-12-24. Retrieved 2022-12-24.
- ^ BBC article suggesting that a "brontobyte" is 1027 bytes
- ^ http://www.sybase.com/content/1031253/EnterpriseUnwired.pdf
- ^ http://www.pcsndreams.com/Pages/Articles/Megabytes.htm
- ^ "(undefined)". MacUser. 7: 362. 1991-02-16. Archived from the original on 2022-12-24.
1 brontobyte (1,000,000,000 megabytes)
- ^ "Hellabytes? A Campaign to Turn Slang into Science". Time. 2010-03-10. Archived from the original on March 13, 2010. Retrieved 2010-05-20.
- ^ Moore, Matthew (2010-03-02). "Hella number: scientists call for new word for 1,000,000,000,000,000,000,000,000,000". The Telegraph. Archived from the original on 2022-12-24. Retrieved 2019-01-04.
More than 20,000 scientists, students and members of the public have signed an online petition backing the new quantity, which would be used for figures with 27 zeros after the first digit.
- ^ "Jargon Watch". Wired. Vol. 18, no. 6. June 2010.
[…] a proposed metric prefix […] useful for describing mega-measurements like Earth's mass (6 Hellagrams). A Facebook petition garnered 30000 signatures
- ^ "The Official Petition to Establish "Hella-" as the SI Prefix for 10^27". Facebook. Retrieved 2010-06-04.
- ^ Kim, Ryan (2010-05-24). "Google gets behind 'hella' campaign". The San Francisco Chronicle. Retrieved 2010-06-04.
- ^ Chawkins, Steve (2010-06-06). "Physics major has a name for a really big number". Los Angeles Times: 2.
- ^ Proceedings of the 19th CGPM (1991), page 80.
- ^ "International System" in Glenn Elert, The Physics Hypertextbook
- ^ Gyllenbok, Jan; Encyclopaedia of Historical Metrology, Weights, and Measures, volume 1, Science Networks Historical Studies 56, Birkhäuser/Springer International Publishing AG, 2010, ISBN 978-3-319-57596-4, page 204
External links
- Moerner Lab Single-Molecule Research Page (Jokingly defines 1 guacamole = 1 / (Avocado's number) of moles. Scientific paper with reference)
- Vendeka.org Home page for the use of the non-SI prefix vendeka to represent 10 to the power of 33, as in vendekabyte.