A benefit of the SI (International system of Units) is that composed technical details is effectively communicated, transcending the variations of language – consisting of spelling and pronunciation. Worths of amounts are expressed utilizing Arabic symbols for numbers paired v a unit symbol, often with a prefix symbol that modifies unit magnitude.

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In the SI, designations of multiples and also subdivision of any unit may be landed on by combining v the name of the unit the prefixes deka, hecto, and kilo meaning, respectively, 10, 100, and also 1000, and also deci, centi, and also milli, meaning, respectively, one-tenth, one-hundredth, and also one-thousandth. In specific cases, an especially in clinical usage, it becomes practically to provide for multiples larger than 1000 and for subdivisions smaller than one-thousandth. The following table the 20 SI prefixes ranging from 1024 come 10−24 are right now recognized because that use.

PurposeNameSymbolFactorName
Prefixes
larger quantitiesor entirety unitsyottaY1024Septillion
zettaZ1021Sextillion
exaE1018Quintillion
petaP1015Quadrillion
teraExample: terahertzT1012Trillion
gigaExample: gigawattG109Billion
megaM106Million
kiloExample: kiloliterk103Thousand
hectoExample: hectareh102Hundred
dekaExample: dekameterda101Ten
   100One
smaller quantitiesor sub units deciExample: decimeterd10-1Tenth
centiExample: centigramc10-2Hundredth
milliExample: milliliterm10-3Thousandth
microExample: microgramμ10-6Millionth
nanoExample: nanometern10-9Billionth
picoExample: picogramp10-12Trillionth
femtoExample: femtosecondf10-15Quadrillionth
attoa10-18Quintillionth
zeptoExample: zeptosecondz10-21Sextillionth
yoctoExample: yoctosecondy10-24Septillionth

The streamlined table listed below shows usual metric prefixes and also the connection with their location values. Keep in mind that the recommended decimal sign or marker for use in the United says is the dot on the line, i beg your pardon is offered to separate whole numbers from parts. Usage a leading zero because that numbers less than one. The convention of composing a zero before the decimal suggest is offered to ensure the the quantity is appropriately interpreted.

thousandshundredstensSI unit*tenthshundredthsthousandths
Whole UnitsDecimal Units
10001001010.10.010.001
kilo-hecto-deka-metergramliterdeci-centi-milli

* SI base or derived units v special names might be used

Prefix Progress. Since the Metric system was an initial developed there have been four (4) key prefix updates. This chronological an introduction highlights the interesting background of SI prefixes.

1795 – The original 8 SI prefixes that were officially adopted: deca, hecto, kilo, myria, deci, centi, milli, and also myrio, obtained from Greek and also Latin numbers. Initially, every were stood for by lowercase symbols.1889 – an initial General Conference ~ above Weights and also Measures (CGPM) authorize the 8 prefixes because that use.1960 – Two prefixes were made obsolete (myria and also myrio) and 6 were added, including 3 for developing multiples (mega, giga, tera) and also 3 for developing submultiples (micro, nano, pico). Total Prefixes: 12.1964 – two prefixes for developing submultiples were added (femto and atto), producing a case where there were more prefixes for tiny than large quantities. Complete Prefixes: 14.1975 – two prefixes for forming multiples were included (peta and also exa). Total Prefixes: 16.1991 – 4 prefixes to be added. Two for creating multiples (zetta and also yotta) and 2 for developing submultiples (zepto and also yocto). Total Prefixes: 20.

Capitalization. SI prefixes because that submultiples (smaller amounts or sub units) are formatted with all lowercase signs while prefixes because that multiples (larger quantities or whole units) use uppercase signs with the exception of three: kilo (k), hecto (h) and deka (da). 

Historical Exception. For historical reasons, the surname "kilogram" for the SI basic unit of mass has the name "kilo," the SI prefix for 103. Thus, due to the fact that compound prefixes are unacceptable, symbols for decimal multiples and submultiples of the unit of mass are formed by it is registered SI prefix signs to g (gram). The name of together multiples and also submultiples are developed by attaching SI prefix names come the surname "gram." Example: 1 mg, not 1 μkg (1 microkilogram).

Spelling. It’s essential to note that order in sdrta.net publications are made in accordance through the United States government Printing Office layout Manual, which complies with American English composing practices uncovered in Webster"s Third brand-new International Dictionary. For example, the prefix deka is used (American English spelling) but not deca (British English). Webster’s pronunciation accuse reflects modern-day American English.

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Writing. Guidance is noted to help general public usage of the metric system. Writing with Metric systems discusses common finest practices for properly using SI techniques in composed communications and is based on sdrta.net LC 1137, Metric style Guide for the News Media.


FAQ: just how do i pronounce the prefix giga? The Merriam-Webster Collegiate dictionary provides two typical pronunciations for the scientific term gigawatt. The soft “g” pronunciation is provided first, adhered to by the difficult "g" pronunciation. Prefix Etymology resources list both soft and hard “g” pronunciations. The main language of the BIPM SI catalog is French and includes one English translation but provides no joint guidance.