Non-SI unit prefix
Encyclopedia
A number of unit prefixes, similar to the standardized SI prefix
es, have been used or proposed by various sources, but which are not part of the International System of Units
(SI).
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,
denoting a factor of , originated from the Greek μύριοι (mýrioi), that is, myriad
, for ten thousand, and the prefixes demi- and double-, denoting a factors of 1/2 and 2 respectively, 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).
One unofficial prefix is bronto-, which has been used in the term brontobyte to represent anything from 1015 to 1027 bytes. SI has already produced standard prefixes for 1015 (peta
), 1021 (zetta
) and 1024 (yotta
).
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. An internet petition has lobbied for the usage of the prefix "hella-" for 1027, a movement that began on the campus of UC Davis.
Centili- (Cen) 10600 (highest lexicographically accepted named number in the system of successive powers of ten as the centillion
, first recorded in 1852, in Europe
an 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)
lako- (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')
yi- (y) 10−5 (Chinese yì 'hundred-thousand')
tini- (ti) 10−5 (Middle English tine 'tiny')
angstro- (å) 10−10 (from metric angstrom, 10−10 meters)
kei 1016
gai 1020
jō 1028
kō 1032
sei 1040
sai 1044
goku 1048
gōgasha 1052
asōgi 1056
nayuta 1060
fukashigi 1064
muryōtaisū 1068
yì 105
jīng 107
ráng 1010
gōu 1011
zhēng 1013
zài 1014
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"
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)
Uni- (U-) In reference to Universe.
Ultra- (Ul-)
Supra- (S-)
Macro- (Ma-)
es to be used for such purposes (e.g., kibi for 210=1024). These units have been accepted and recommended by all international standards bodies.
SI prefix
The International System of Units specifies a set of unit prefixes known as SI prefixes or metric prefixes. An SI prefix is a name that precedes a basic unit of measure to indicate a decadic multiple or fraction of the unit. Each prefix has a unique symbol that is prepended to the unit symbol...
es, have been used or proposed by various sources, but which are not part of the International System of Units
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
(SI).
Former metric prefixes
250pxSome prefixes were used in older versions of the metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
but are not part of the modern metric system, the SI
International System of Units
The International System of Units is the modern form of the metric system and is generally a system of units of measurement devised around seven base units and the convenience of the number ten. The older metric system included several groups of units...
.
The prefix myria,
denoting a factor of , originated from the Greek μύριοι (mýrioi), that is, myriad
Myriad
Myriad , "numberlesscountless, infinite", is a classical Greek word for the number 10,000. In modern English, the word refers to an unspecified large quantity.-History and usage:...
, for ten thousand, and the prefixes demi- and double-, denoting a factors of 1/2 and 2 respectively, were parts of the original metric system
Metric system
The metric system is an international decimalised system of measurement. France was first to adopt a metric system, in 1799, and a metric system is now the official system of measurement, used in almost every country in the world...
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
Sweden
Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....
(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
Mile
A mile is a unit of length, most commonly 5,280 feet . The mile of 5,280 feet is sometimes called the statute mile or land mile to distinguish it from the nautical 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
Avoirdupois
The avoirdupois system is a system of weights based on a pound of 16 ounces. It is the everyday system of weight used in the United States and is still widely used to varying degrees by many people in Canada, the United Kingdom, and some other former British colonies despite the official adoption...
unit, the quarter (25 pounds). (see also myriogramme
Myriogramme
Myriogramme is a genus of red alga comprising approximately 34 species.- Species :The species currently recognised are:*M. alliacea*M. caespitosa*M. carnea*M. cartilaginea*M. ciliata*M. costata...
, a genus of seaweed
Seaweed
Seaweed is a loose, colloquial term encompassing macroscopic, multicellular, benthic marine algae. The term includes some members of the red, brown and green algae...
). In Isaac Asimov
Isaac Asimov
Isaac Asimov was an American author and professor of biochemistry at Boston University, best known for his works of science fiction and for his popular science books. Asimov was one of the most prolific writers of all time, having written or edited more than 500 books and an estimated 90,000...
's novel Foundation and Empire
Foundation and Empire
Foundation and Empire is a novel written by Isaac Asimov that was published by Gnome Press in 1952. It is the second book published in the Foundation Series, and the fourth in the in-universe chronology...
, 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).
Unofficial prefixes
There are many unofficial or fabricated metric prefixes circulating the internet, especially for values smaller than 10−24 or larger than 1024.One unofficial prefix is bronto-, which has been used in the term brontobyte to represent anything from 1015 to 1027 bytes. SI has already produced standard prefixes for 1015 (peta
Peta (prefix)
Peta- is a prefix in the metric system denoting 1015 or . For example:1 petametre = 1015 metres1 petasecond = 1015 seconds...
), 1021 (zetta
Zetta
Zetta- is a prefix in the metric system denoting a factor of 1021 or .Added to the SI in 1991, it is evocative of the French numeral sept, meaning seven, because it is equal to 10007....
) and 1024 (yotta
Yotta
Yotta is the largest unit prefix in the International System of Units denoting a factor of 1024 or . It has the unit symbol Y.The prefix name is derived from the Greek , meaning eight, because it is equal to 10008...
).
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. An internet petition has lobbied for the usage of the prefix "hella-" for 1027, a movement that began on the campus of UC Davis.
Other proposed prefixes
omni- (Om) 101000Centili- (Cen) 10600 (highest lexicographically accepted named number in the system of successive powers of ten as the centillion
Centillion
Centillion is a big number. It refers to different quantities based on locality of usage.- North American system :* In Canadian and U.S. usage, two centillion is 10303+10303....
, first recorded in 1852, in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
an traditional usage; alternatively it can be 10303 in U.S. and Canadian usage)
Googol
Googol
A googol is the large number 10100, that is, the digit 1 followed by 100 zeros:The term was coined in 1938 by 9-year-old Milton Sirotta , nephew of American mathematician Edward Kasner...
- (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)
lako- (l) 105 (Indian English lakh
Lakh
A lakh is a unit in the Indian numbering system equal to one hundred thousand . It is widely used both in official and other contexts in Pakistan, Bangladesh, India, Maldives, Nepal, Sri Lanka, Myanmar and is often used in Indian English.-Usage:...
, 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')
yi- (y) 10−5 (Chinese yì 'hundred-thousand')
tini- (ti) 10−5 (Middle English tine 'tiny')
angstro- (å) 10−10 (from metric angstrom, 10−10 meters)
Japanese large numbers
oku 108kei 1016
gai 1020
jō 1028
kō 1032
sei 1040
sai 1044
goku 1048
gōgasha 1052
asōgi 1056
nayuta 1060
fukashigi 1064
muryōtaisū 1068
Chinese large numbers
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 1048héng 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 Chinese numerals
These 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 prefixes without a set factor higher than exa
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 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 prefixBinary prefix
In computing, a binary prefix is a specifier or mnemonic that is prepended to the units of digital information, the bit and the byte, to indicate multiplication by a power of 2...
es to be used for such purposes (e.g., kibi for 210=1024). These units have been accepted and recommended by all international standards bodies.
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.