Unit prefix
A number of unit prefixes, similar to the standardized SI prefixes, have been used or proposed by various sources, but which are not part of the International System of Units (SI).
Former metric prefixes
Some prefixes were used in older versions of the metric system but are not part of the modern metric system, the SI.
The prefix myria, [1] [2] denoting a factor of 10000, originated from the Greek μύριοι (mýrioi) for ten thousand, and the prefixes demi- and double-, denoting a factors of 1/2 and 2 respectively,[3] were parts of the original metric system adopted in France in 1795, but they were not retained when the SI prefixes were agreed internationally by the 11th CGPM conference in 1960. They were dropped because they were not decimal, nor symmetrical. They were rarely used, though the myriameter (10 km) is occasionally encountered in 19th-century train tariffs, or in some classifications of wavelengths as the adjective myriametric. In Sweden (and possibly elsewhere), the myriameter is still very common in everyday use (although not recognized or used officially). In Swedish this unit is called 'mil', sometimes causing confusion when Swedes use the English word 'mile' (incorrectly) as a direct translation. Of units customarily used in trade in France, the myriagramme (10 kg) was the metric replacement for an avoirdupois unit, the quarter (25 pounds). (see also myriogramme, a genus of seaweed). In Isaac Asimov's novel Foundation and Empire, there is a mention of the myriaton.
Also obsolete are metric double prefixes, such as those formerly used in micromillimetres (now nanometres), micromicrofarads (now picofarads), hectokilometres (also in the derived adjective hectokilometric typically used for qualifying the fuel consumption measures).[4]
Unofficial prefixes
There are many unofficial or fabricated metric prefixes circulating the internet, especially for values smaller than 10−24 or larger than 1024. [5] [6] One well-known unofficial prefix is bronto-, used in the term brontobyte to represent 1027. SI has already produced standard prefixes for 1015 (peta), 1021 (zetta) and 1024 (yotta).[7][8][9][10][11]
The z and y on the extreme prefixes zepto-, yocto- and Zetta-, Yotta- suggest the start of a series backwards through the alphabet. Following the initial letters are distorted Greek numerals (h)epta- and octa-. This pattern has been extended further, with the terms xenno-, weko-, vendeko- and xenna-, weka-, vendeka- from Greek ennea-, deka-, endeka-; sometimes a t is added for greater differentiation, though both xento-, wekto- etc. and xenta-, wekta- etc. have been proposed.[12] An internet petition has lobbied for the usage of the prefix "hella-" for 1027, a movement that began on the campus of UC Davis.[13]
Other proposed prefixes are:
omni- (Om) 101000
Centili- (Cen) 10600 (highest lexicographically accepted named number in the system of successive powers of ten as the centillion, first recorded in 1852, in European traditional usage; alternatively it can be 10303 in U.S. and Canadian usage)
Googol- (Goo) 10100 (highest known power accepted in Western Scientific field)
Asankhyeya- (Asa-) 10140 (highest number outside the decimal notation of the Buddhist work of Jain in 100 BC)
laco- (l) 105 (Indian English lakh, lac 'hundred-thousand', from Pali [lakʰ])
ribo- (r) 104 (Hebrew ribo 'ten-thousand', from highest Aramaic number)
myri- (my) 10−4 (modifying the discontinued metric prefix myrio- 'ten-thousandth', from Latin myrias 'ten-thousand', from Greek murioi)
mini- (mi) 10−4 (Latin minimus, 'smallest', the superlative of parvus 'small')
tini- (ti) 10−5 (Middle English tine 'tiny')
angstro- (a) 10−10 (angstrom, 10−10 meters)
Large Numbers from Japan:
oku 108
kei 1016
gai 1020
jō 1028
kō 1032
sei 1040
sai 1044
goku 1048
gōgasha 1052
asōgi 1056
nayuta 1060
fukashigi 1064
muryōtaisū 1068
Large numbers from Chinese numerals:
wàn 104 A group for ten thousand.
yì 105
jīng 107
ráng 1010
gōu 1011
zhēng 1013
zài 1014
Large Numbers from Buddhism found in Chinese numerals:
jí 1048
héng hé shā 1052 Literally means "Sands of the Ganges"; a metaphor used in a number of Buddhist texts referring to the grains of sand in the Ganges River.
ā sēng qí 1056 From Sanskrit Asaṃkhyeya
nà yóu tā 1060 From Sanskrit Nayuta
bùkě sīyì 1064 Literally translated as "unfathomable".
wú liàng 1068 Literally translated as "without measure"
dà shù 1072 Literally translated as "a large number"
Small Numbers from Japan
sen 10−7
sha 10−8
Small Numbers from Chinese numerals, though they have fallen into disuse by the Chinese :
miǎo 10−11 (Ancient Chinese)
āi 10−10 (Ancient Chinese) A good alternative for angstrom.
shā 10−8 (Ancient Chinese)
qiān 10−7 (Ancient Chinese)
hū 10−5 (Ancient Chinese)
sī 10−4 (Ancient Chinese)
Other Possible prefexs without a set factor higher than Exa are:
Super- (Su-)
Uni- (U-) In reference to Universe.
Ultra- (Ul-)
Supra- (S-)
Macro- (Ma-)
IEC binary prefixes
Owing to the frequent ambiguous and confusing use of standard SI prefixes in the information technology field[14] to represent unit multiples of powers of two, rather than powers of ten (e.g., the use of kilo for 210=1024, rather than 1000), the International Electrotechnical Commission introduced a set of new, but similarly named, binary prefixes to be used for such purposes (e.g., kibi for 210=1024). These units have been accepted and recommended by all international standards bodies.
See also
References
- ^
29th Congress of the United States, Session 1 (1866-05-13). "H.R. 596, An Act to authorize the use of the metric system of weights and measures".
{{cite web}}: CS1 maint: numeric names: authors list (link) - ^ D. Brewster (1830). The Edinburgh Encyclopaedia. p. 494.
- ^ histoire.du.metre.free.fr
- ^ Rowlett, Russ (2010-05-28). "millimicro-". How Many? A Dictionary of Units of Measurement. Retrieved 2010-10-30.
{{cite encyclopedia}}: More than one of|author=and|last=specified (help) - ^ Gerard P. Michon. "Current and Deprecated Prefixes".
- ^ Gerard P. Michon. "Funny prefixes & dubious proposals (updated yearly)".
- ^ BBC article suggesting that a brontobyte is 1027 bytes
- ^ Sybase article suggesting that a brontobyte is 1024 or 1027 bytes (Note article's table a few pages down. Note also it mistakenly places 1 terabyte = 1,000 megabytes. It should be 1 terabyte = 1,024 gigabytes. Also yottabyte is shown incorrectly as zottabyte. With those corrections, it also is clearly 1027.)
- ^ Article suggesting that a brontobyte is 1021 bytes
- ^ Article suggesting that a brontobyte was 1015 bytes before the creation of the prefix peta- (Article is of dubious authority and suggests that Greek letters ν, π, and φ are SI prefixes for nano-, pico-, and femto-, instead of n, p, and f.)
- ^ Article suggesting that brontobyte is 1027 bytes
- ^ "International System" in Glenn Elert, The Physics Hypertextbook
- ^ "Hellabytes? A Campaign to Turn Slang into Science". Time. 2010-03-10. Retrieved 2010-05-20.
- ^ Prefixes for binary multiples at International Electrotechnical Commission
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.