An SI prefix (also known as a metric prefix) is a name or associated symbol that precedes a unit of measure (or its symbol) to form a decimal multiple or submultiple. The decimal ( base ten or occasionally denary) Numeral system has ten as its base. In Mathematics, a multiple of an Integer is the product of that integer with another integer The abbreviation SI is from the French language name Système International d’Unités (also known as International System of Units). SI prefixes are used to reduce the quantity of zeroes in numerical equivalencies. An affix is a Morpheme that is attached to a stem to form a word For example, one-billionth of an ampere (a small electrical current) can be written as 0. 000 000 001 ampere. In symbol form, this is written as 0. 000 000 001 A. Using an SI prefix, these are equivalent to 1 nanoampere or 1 nA. The SI prefixes are governed by the Bureau International des Poids et Mesures (BIPM, also known as the International Bureau of Weights and Measures) and are the product of four resolutions dating from 1960 to 1991. The International Bureau of Weights and Measures ( Bureau international des poids et mesures, in French) is an international Standards organization, one

Contents 1 List of SI prefixes 2 Usage 2.1 General use of prefix names and symbols 2.2 Prohibition of multiple prefixes 2.3 SI prefixes with symbols for time and angles 2.4 SI prefixes with °C 3 Details 4 Pronunciation 5 Use outside SI 5.1 Non-SI units 5.2 Computing 6 Proposed changes 6.1 Extension 6.2 Harmonisation 7 See also 8 References 9 External links 9.1 Standards organisations 9.2 Other proposals

List of SI prefixes

The twenty SI prefixes are shown in the chart below.

SI prefixes

1000m	10n	Prefix	Symbol	Since[1]	Short scale	Long scale	Decimal
10008	1024	yotta-	Y	1991	Septillion	Quadrillion	1 000 000 000 000 000 000 000 000
10007	1021	zetta-	Z	1991	Sextillion	Trilliard	1 000 000 000 000 000 000 000
10006	1018	exa-	E	1975	Quintillion	Trillion	1 000 000 000 000 000 000
10005	1015	peta-	P	1975	Quadrillion	Billiard	1 000 000 000 000 000
10004	1012	tera-	T	1960	Trillion	Billion	1 000 000 000 000
10003	109	giga-	G	1960	Billion	Milliard	1 000 000 000
10002	106	mega-	M	1960	Million		1 000 000
10001	103	kilo-	k	1795	Thousand		1 000
10002/3	102	hecto-	h	1795	Hundred		100
10001/3	101	deca-	da	1795	Ten		10
10000	100	(none)	(none)	NA	One		1
1000−1/3	10−1	deci-	d	1795	Tenth		0. The long and short scales are two different numerical systems used throughout the world Short scale is the English translation of the French The long and short scales are two different numerical systems used throughout the world Short scale is the English translation of the French The decimal ( base ten or occasionally denary) Numeral system has ten as its base. yotta- (symbol Y) is an SI prefix in the SI ( System of units) denoting 1024 or 1 000 000 000 000 000 000 000 000 Names of numbers larger than a quadrillion are almost never used for reasons discussed further below This list compares various sizes of positive Numbers including counts of things Dimensionless quantity and probabilities. zetta- (symbol Z) is an SI prefix in the SI ( System of units) denoting 1021 or 1 000 000 000 000 000 000 000 Names of numbers larger than a quadrillion are almost never used for reasons discussed further below Names of numbers larger than a quadrillion are almost never used for reasons discussed further below exa- (symbol E) is a prefix in the SI system of units denoting 1018 or 1 000 000 000 000 000 000 Names of numbers larger than a quadrillion are almost never used for reasons discussed further below This list compares various sizes of positive Numbers including counts of things Dimensionless quantity and probabilities. In Physics and Mathematics, peta- (symbol P) is a prefix in the SI ( System of units) denoting 1015 This list compares various sizes of positive Numbers including counts of things Dimensionless quantity and probabilities. Names of numbers larger than a quadrillion are almost never used for reasons discussed further below teras- (symbol T) is a prefix in the SI system of units denoting 1012, or 1000000000000 (1 trillion This list compares various sizes of positive Numbers including counts of things Dimensionless quantity and probabilities. For other meanings see Giga (disambiguation Giga- (symbol G is a prefix in the SI system of units denoting 109 Milliard is a French -derived word meaning the number 1000000000 (109 one thousand million SI prefix Giga) Mega- (symbol M) is an SI prefix in the SI system of units denoting a factor of 106, 1000000 (one Million Kilo- (symbol k is a prefix in the SI and other systems of units denoting 103 or 1000 hecto- or hecta- (symbol h) is a SI prefix in the SI system of units denoting a factor of 102 (100 deca- or deka- is an SI prefix (symbol da) in the SI system of units also a Numerical prefix (from Greek δέκα Mathematics For any number x: x ·1 = 1· x = x (1 is the multiplicative identity deci- (symbol d) is a prefix in the SI system of units denoting a factor of 10−1 (1/10 1
1000−2/3	10−2	centi-	c	1795	Hundredth		0. centi- (symbol c) is a SI prefix in the SI system of units denoting a factor of 10−2 or 1/100 01
1000−1	10−3	milli-	m	1795	Thousandth		0. "Milli" redirects here for the village in Azerbaijan see Birinci Milli; for similar-sounding words see Millie. 001
1000−2	10−6	micro-	µ	1960[2]	Millionth		0. micro- ( µ) is a prefix in the SI and other systems of units denoting a factor of 10&minus6 (one Millionth. 000 001
1000−3	10−9	nano-	n	1960	Billionth	Milliardth	0. nano- is a prefix (symbol n) in the SI system of units denoting a factor of 10−9 000 000 001
1000−4	10−12	pico-	p	1960	Trillionth	Billionth	0. pico- (symbol p) is a prefix denoting a factor of 10-12 in the International System of Units (SI 000 000 000 001
1000−5	10−15	femto-	f	1964	Quadrillionth	Billiardth	0. femto- is an SI prefix (symbol f) in the SI system of units denoting a factor of 10−15 or 0 000 000 000 000 001
1000−6	10−18	atto-	a	1964	Quintillionth	Trillionth	0. atto- (symbol a) is an SI prefix to a unit and means that it is 10−18 times this unit 000 000 000 000 000 001
1000−7	10−21	zepto-	z	1991	Sextillionth	Trilliardth	0. zepto- (symbol z) is a prefix in the SI system of units denoting a factor of 10−21 000 000 000 000 000 000 001
1000−8	10−24	yocto-	y	1991	Septillionth	Quadrillionth	0. yocto- (symbol y) is an SI prefix in the SI system of units denoting a factor of 10−24 or 0 000 000 000 000 000 000 000 001
The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM. The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures ( CGPM, never GCWM The 1948 recognition of the micron by the CGPM was abrogated in 1967. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre

Usage

General use of prefix names and symbols

Twenty SI prefixes are available to combine with units of measure. For example, the prefix name kilo denotes a multiple of one thousand, so 1 kilometre equals 1000 metres, 1 kilogram equals 1000 grams, 1 kilowatt equals 1000 watts, and so on. The kilometre ( American spelling: kilometer) symbol km is a unit of Length in the Metric system, equal to one thousand The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International For other uses of the words gram or gramme see Gram (disambiguation. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. Each SI prefix name has an associated symbol which can be used in combination with the symbols for units of measure. Thus, the “kilo” symbol, k, can be used to produce km, kg, and kW, (kilometre, kilogram, and kilowatt). SI prefixes are internationally recognized and also exist outside the SI (many of them long pre-date SI, going back to the original introduction of the metric system); prefixes may also be used in combination with non-SI units; for example: milligauss (mG), kilofoot (kft) and microinch (µin).

Prohibition of multiple prefixes

The kilogram is the only SI base unit that has an SI prefix as part of its unit name and symbol. Because multiple prefixes may not be used (such as microkilogram or µkg), the prefixes are used with the unit gram and its symbol g (e. g. milligram or mg).

SI prefixes with symbols for time and angles

Officially endorsed policies of the BIPM and the [American] National Institute of Standards and Technology (NIST) vary slightly with respect to the use of the SI prefixes—both between their respective agencies and from real-world practice. The United States of America —commonly referred to as the For instance, the NIST advises that “…to avoid confusion, prefix symbols (and prefixes) are not used with the time-related unit symbols (names) min (minute), h (hour), d (day); nor with the angle-related symbols (names) ° (degree), ′ (minute), and ″ (second). ” The BIPM’s position on the use of SI prefixes with units of time larger than the second is the same as that of the NIST but their position with regard to angles differs: they state “However astronomers use milliarcsecond, which they denote mas, and microarcsecond, µas, which they use as units for measuring very small angles. ”

SI prefixes with °C

A similar difference between officially endorsed policy and actual practice exists with regard to the symbol for degree Celsius (°C). The NIST states “Prefix symbols may be used with the unit symbol °C and prefixes may be used with the unit name ‘degree Celsius. ’ For example, 12 m°C (12 millidegrees Celsius) is acceptable. ” Notwithstanding this official endorsement, the practice of using prefixed forms of “°C” (such as “µ°C”) has not been well-adopted in science and engineering; prefixed forms of the kelvin are usually used instead. The kelvin (symbol K) is a unit increment of Temperature and is one of the seven SI base units The Kelvin scale is a thermodynamic

Details

See also: Non-SI unit prefixes

Examples:

• 5 cm = 5 × 10⁻² m = 5 × 0. 01 m = 0. 05 m
• 3 MW = 3 × 10⁶ W = 3 × 1 000 000 W = 3 000 000 W

The prefix always takes precedence over any exponentiation; thus "km²" means square kilometre and not kilo–square metre. For example, 3 km² is equal to 3 000 000 m² and not to 3000 m² (nor to 9 000 000 m²). Thus the SI prefixes provide steps of a factor one million instead of one thousand in the case of an exponent 2, of a thousand million in the case of an exponent 3, etc. As a result large numbers may be needed, even if the prefixes are fully used, or intermediate units (like the litre) are introduced. The litre or liter (see spelling differences) is a unit of Volume.

Prefixes where the exponent is divisible by three are often recommended. Hence "100 m" rather than "1 hm".

The obsolete prefixes such as myrio- and myria- were dropped before SI was adopted in 1960, probably because they did not fit this pattern, no one-letter symbol was available (M, m, and µ already being used; the two-letter symbols mo and ma were used instead) and were rarely used anyway.

The prefix kilo derives from the Greek word χίλια (khilia or chilia) = thousand. Greek (el ελληνική γλώσσα or simply el ελληνικά — "Hellenic" is an Indo-European language, spoken today by 15-22 million people mainly

Double prefixes such as those formerly used in micromicrofarads (picofarads), hectokilometres (100 kilometres), and millimicrons or micromillimetres (both nanometres) were also dropped with the introduction of the SI. This is about the capacitance unit of measure For the charge unit see Faraday (unit.

Though in principle legal, many combinations of prefixes with quantities are rarely used. In most contexts only a few, i. e. the most common, standard combination are established:

• Mass: hectogram, gram, milligram, microgram, and smaller are common. However, megagram or larger are rarely used; tonnes or scientific notation are used instead. Scientific notation, also sometimes known as standard form or as exponential notation, is a way of writing numbers that accommodates values too large or small to be Megagram is sometimes used to disambiguate the (metric) tonne from the various (non-metric) tons.
• Volume in litres: litre, decilitre, centilitre, millilitre, microlitre, and smaller are common. Larger volumes are sometimes denoted in hectolitres; otherwise in cubic metres or cubic kilometres. In Australia, large quantities of water are measured in kilolitres, megalitres and gigalitres.
• Length: kilometre, metre, decimetre, centimetre, millimetre, and smaller are common. The micrometre is often referred to by the non-SI term micron. A micrometre ( American spelling: micrometer; symbol µm) is one millionth of a Metre, or equivalently one thousandth of a Millimetre In some fields such as chemistry, the angstrom (equal to 0. Chemistry (from Egyptian kēme (chem meaning "earth") is the Science concerned with the composition structure and properties An ångström or angstrom (symbol Å) (ˈɔːŋstrəm Swedish: ˈɔ̀ŋstrœm is an internationally recognized non- SI unit of length equal 1 nm) competes with the nanometre. The femtometre, used mainly in particle physics, is usually called a fermi. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International At large scales, megametre, gigametre, and larger are rarely used. Often used are astronomical units, light years, and parsecs; the astronomical unit is mentioned in the SI standards as an accepted non-SI unit. The astronomical unit ( AU or au or au or sometimes ua) is a unit of Length based on the distance from the Earth to the A light-year or light year (symbol ly) is a unit of Length, equal to just under ten trillion Kilometres As defined by History The first direct measurements of an object at interstellar distances were undertaken by German Astronomer Friedrich Wilhelm Bessel in 1838
• Time: second, millisecond, microsecond, and shorter are common. The kilosecond and megasecond also have some use, though for these and longer times one usually uses either scientific notation or minutes, hours, and so on.

^† the United Kingdom, Ireland, Australia and New Zealand previously used the long scale number name conventions, but have now at least partly switched to the short scale usage. The long and short scales are two different numerical systems used throughout the world Short scale is the English translation of the French The long and short scales are two different numerical systems used throughout the world Short scale is the English translation of the French In particular, above a million and below a millionth, the same name has different values in the two naming systems, so billion and trillion (for example) have unfortunately become potentially ambiguous terms internationally. Using the SI prefixes can circumvent this problem.

Pronunciation

There are two accepted pronunciations for the prefix giga-: [ˈgɪgə] and [ˈdʒɪgə]. According to the American writer Self, in the 1920s a German committee member of the International Electrotechnical Commission proposed giga- as a prefix for 10⁹, drawing on a verse by the humorous poet Christian Morgenstern that appeared in the third (1908) edition of Galgenlieder (Gallows Songs). The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes This suggests a hard German g was originally intended as the pronunciation. Self was unable to ascertain at what point the /dʒ/ (soft g) pronunciation became accepted, but as of 1995 current practice had returned to /g/ (hard g). ^{[1] [2]}

When any SI prefix is affixed to a root word, the prefix carries the primary stress, and the root word carries a secondary stress on the same syllable that is stressed when the root word stands alone. In Linguistics, stress is the relative emphasis that may be given to certain Syllables in a word For example, the pronunciation and stress of gigabyte is /ˈɡɪɡəbaɪt/. A gigabyte (derived from the SI prefix Giga-) is a unit of Information or Computer However, when a word with an SI prefix is also commonly used outside the scientific community, it may adopt other pronunciations that do not follow this rule. For example, kilometre (or in the USA, kilometer) may also be pronounced /kɨˈlɒmɨtɚ/.

Use outside SI

The symbol "K" is often used informally to mean a multiple of (a) thousand, so one may talk of "a 40K salary" (40 000), or the Y2K problem. The Year 2000 problem (also known as the Y2K problem, the millennium bug, the Y2K bug, or simply Y2K) was a notable Computer bug resulting In these cases an uppercase K is often used, although using an uppercase K is never correct when writing under the rules of the SI. Also, it is often used as a prefix to designate the binary prefix kilo = 2¹⁰ = 1024, although this is now non-standard. In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two

Non-SI units

• Prefixes go back to the introduction of the metric system in the 1790s, long before the SI was introduced in 1960. The metric system is a decimalised system of measurement. It exists in several variations with different choices of base units, though the choice of base units does The prefixes (including those introduced after the introduction of SI) are used with any metric units, SI or not (e. g. millidynes).
• SI prefixes rarely appear coupled with imperial units or English units except in some specialised cases (e. Imperial units or the Imperial system is a collection of units first defined in the British Weights and Measures Act of 1824 English unit is the American name for a unit in one of a number of systems of Units of measurement, some obsolete and some still in use in present-day USA, the g. microinches, kilofeet, kilopound or 'kip').
• They are also used with other specialized units used in particular fields (e. g. megaelectronvolts, gigaparsecs).
• They are also occasionally used with currency units (e. g. , gigadollar), mainly by people who are familiar with the prefixes from scientific usage.

Computing

Main article: Binary prefix

The prefixes k and greater are common in computing, where they are applied to information and storage units like the bit and the byte. In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two Computing is usually defined like the activity of using and developing Computer technology Computer hardware and software. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. Since 2¹⁰ = 1024, and 10³ = 1000, this led to the SI prefix letters being used to denote "binary" powers. Although these are incorrect usages according to the SI standards it seems common to apply base 10 prefixes, when relating to computer memory, as follows:

k

= 2¹⁰ = 1 024

M

= 2²⁰ = 1 048 576

G

= 2³⁰ = 1 073 741 824

T

= 2⁴⁰ = 1 099 511 627 776

P

= 2⁵⁰ = 1 125 899 906 842 624

These prefixes, however, usually retain their powers-of-1000 meanings when used to describe either disk storage or rates of data transmission (bit rates): 10 Mbit/s Ethernet runs at 10,000,000 bit/s, not 10,485,760 bit/s. In Telecommunications and Computing, bitrate (sometimes written bit rate, data rate or as a Variable R or f b In telecommunications Bit rate or Data transfer rate is the average number of Bits characters or blocks per unit time passing between equipment in a data transmission Ethernet is a family of frame -based Computer networking technologies for Local area networks (LANs The confusion is compounded by the fact that the units of information (the bit and the byte) are not part of SI, where the bit, byte, octet, baud or symbol rate would rather be given in hertz. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. In Computing, an octet is a grouping of eight Bits Octet, with the only exception noted below always refers to an entity having exactly eight In Telecommunications and Electronics, baud (ˈbɔːd unit symbol "Bd" is synonymous to symbols/s or pulses/s. In Digital communications, symbol rate, also known as baud or modulation rate is the number of symbol changes (signalling events made to the transmission medium per second The hertz (symbol Hz) is a measure of Frequency, informally defined as the number of events occurring per Second. Although some use "bit" for the bit and "b" for the byte, "b" is often used for bit and "B" for byte instead. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication A byte (pronounced "bite" baɪt is the basic unit of measurement of information storage in Computer science. It is recommended by several standards bodies to use bit and B to keep the units very distinct, as in kbit or MiB. French-speakers often use "o" for "octet", today a near synonym for the byte.

Consequently, the International Electrotechnical Commission (IEC) adopted new binary prefixes in 1998, formed from the first syllable of the decimal prefix plus 'bi' (pronounced 'bee'). The International Electrotechnical Commission ( IEC) is a not-for-profit, non-governmental international Standards organization that prepares and publishes In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two The symbol is the decimal symbol plus 'i'. So now, one kilobyte (1 kB) equals 1000 bytes, whereas one kibibyte (1 KiB) equals 2¹⁰ = 1024 bytes. A kilobyte (derived from the SI prefix Kilo -, meaning 1000 is a unit of Information or Computer storage equal to either 1024 A kibibyte (a contraction of ki lo bi nary byte) is a unit of Information or Computer storage, established by the International Likewise mebi (Mi; 2²⁰), gibi (Gi; 2³⁰), tebi (Ti; 2⁴⁰), pebi (Pi; 2⁵⁰), and exbi (Ei; 2⁶⁰). In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two Although the IEC standard does not mention them, the sequence can be readily extended to zebi (Zi; 2⁷⁰) and yobi (Yi; 2⁸⁰). In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two The practical use of these binary prefixes is growing only very slowly and is largely limited to expert literature. They remain mostly ignored by marketing literature.

Proposed changes

Extension

Continuing backwards in the alphabet, after zetta and yotta, proposals for the next large number include xenta and xona (among others), the latter as an alteration of the Latin-derived numerical prefix nona-, and the next small number would also start with an ‘x’. Latin ( lingua Latīna, laˈtiːna is an Italic language, historically spoken in Latium and Ancient Rome. Numerical prefixes are usually derived from the words for numbers in various languages most commonly Greek and Latin, although this is not always the case

One proposed extension is, after zetta and yotta, xona, weka, vunda, uda, and treda. ^[3]

Preserving the rule on abbreviating the prefixes (a Latin capital for the large number and a lower-case letter for the small number), even without consensus on the full name the following prefix symbols could be used without ambiguity: ‘X’, ‘W’, ‘V’, ‘x’, ‘w’, ‘v’. The logically next small prefix symbol, ‘u’, was formerly the accepted substitution for ‘µ’ (now withdrawn), the symbol for “micro”. ^[4][5]

Another proposal for xenta/xona is novetta, from the Italian nove. This does not have the convenience of backward alphabetic order. Also, the symbol 'n' is already in use for "nano".

Harmonisation

There are also proposals for further harmonisation of the capitalisation. Therefore the symbols for kilo, hecto, and deka would be changed from ‘k’ to ‘K’, from ‘h’ to ‘H’, and from ‘da’ to ‘D’. Likewise some lobby for the removal of prefixes that do not fit the 10^±3n scheme, namely hecto, deka, deci, and centi. The CGPM has postponed its decision on both matters for now. The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures ( CGPM, never GCWM

An unsolved (and maybe unsolvable) issue is the application of prefixes to units with exponents other than ±1. The prefix is always applied before the exponent. This eventually led to the introduction of special units for area and volume without exponents in the original metric system:

• 1 are (a) = 100 m² (10 m × 10 m = 1 dam × 1 dam = 1 dam²)
  • ⇒ 1 ca = 1 m² (1 m × 1 m)
  • ⇒ 1 ha = 10 000 m² (100 m × 100 m = 1 hm × 1 hm = 1 hm²)
• 1 stere (st) = 1 m³
• 1 litre (l or L) = 1 dm³ = 1 mst = 0. The metric system is a decimalised system of measurement. It exists in several variations with different choices of base units, though the choice of base units does Conversions One are is equivalent to Metric 00001 km2 (square kilometres 0 The stère is a measurement unit for Volume of wood and equals one Cubic metre. The litre or liter (see spelling differences) is a unit of Volume. 001 m³

Of these the litre and the hectare are the most ubiquitous in common use: Litre designations are sometimes used to differentiate a volume of liquid (as opposed to a gas, or solid which are usually designated as cubic volumes). Hectares are widely used as a metric alternative to the acre (approximately 2. 5 acres to the hectare).

See also

References

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL. In computing binary prefixes are names or associated symbols that can precede a unit of measure (such as a Byte) to indicate multiplication by a power of two Engineering notation is a version of Scientific notation in which the power of ten must be a multiple of three (i The metric system is a decimalised system of measurement. It exists in several variations with different choices of base units, though the choice of base units does In Linguistics, a number name, or numeral, is a symbol or group of symbols or a Word in a Natural language that represents a Number The following tables list the names and symbols for the numbers 0 through 10 in various Languages and scripts of the world An order of magnitude is the class of scale or magnitude of any amount where each class contains values of a fixed ratio to the class preceding it Scientific notation, also sometimes known as standard form or as exponential notation, is a way of writing numbers that accommodates values too large or small to be The International System of Units (SI defines seven dimensionally independent SI base units. SI derived units are part of the SI system of measurement units and are derived from the seven SI base units They are derived from SI basic units/defined The Free On-line Dictionary of Computing ( FOLDOC) is an online searchable encyclopedic Dictionary of Computing subjects The GNU Free Documentation License ( GNU FDL or simply GFDL) is a Copyleft License for free documentation designed by the Free Software

External links

Standards organisations

• The International Bureau of Weights and Measures (BIPM): SI prefixes
• US NIST "Definitions of the SI units: The twenty SI prefixes"
• US NIST "Definitions of the SI units: The binary prefixes"
• International Standard ISO 2955: "Information processing - Representation of SI and other units in Systems with limited Character sets"

Other proposals

• Proposal for an extension of the SI-prefix system to even larger and smaller units

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