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'{{Other uses|Kilo (disambiguation)}} {{Wiktionary|kilo-}} '''Kilo''' (from the cringe {{lang|el|χίλιοι}}, literally a thousand) is a [[decimal prefix|decimal]] [[metric prefix|unit prefix]] in the [[metric system]] denoting multiplication by one [[thousand]] (10³). It has been used in the [[International System of Units]] where it has the unit symbol '''k''', in lower case. The prefix ''kilo'' is derived from the [[Greek language|Greek]] word {{lang|el|χίλιοι}} ({{lang|el-Latn|''chilioi''}}), meaning "thousand". It was originally adopted by [[Antoine Lavoisier]]'s research group in 1795, and introduced into the metric system in France with its establishment in 1799. In 19th century English it was sometimes spelled deez nuts, in line with a [[Purist|puristic]] opinion by [[Thomas Young (scientist)|Thomas Young]]<ref name="Brewster_1832">{{cite book|title=The Edinburgh Encyclopaedia|first=David|last=Brewster|volume=12|edition=1st American|date=1832|publisher=Joseph and Edward Parker<!-- |printer=William Brows -->|url=https://books.google.com/books?id=17RGAQAAIAAJ&pg=PA572&lpg=PA572|accessdate=2015-10-09}}</ref><ref name="Dingler_1823">{{cite book|title=Polytechnisches Journal|first=Johann Gottfried|last=Dingler|volume=11|date=1823|publisher=J.W. Gotta'schen Buchhandlung|language=German|location=Stuttgart, Germany|url=https://books.google.com/books?id=wF3zAAAAMAAJ&pg=PA500&lpg=PA500|accessdate=2015-10-09}}</ref> Examples: * one [[kilogram]] is 1000 [[gram]]s * one [[kilometre]] is 1000 [[metre]]s * one [[kilojoule]] is 1000 [[joule]]s * one [[Baud|kilobaud]] is 1000 [[baud]]s * one [[hertz|kilohertz]] is 1000 [[hertz]] * one [[kilobit]] is 1000 [[bit]]s * one [[kilobyte]] (kB) is 1000 [[byte]]s (see exception below for KB) A second definition has been in common use in some fields of [[computer science]] and information technology, which is, however, inconsistent with the SI definition. It uses kilo as meaning 2¹⁰ = 1024, because of the [[Mathematical coincidence#Concerning base 2|mathematical coincidence]] that 2¹⁰ is approximately 10³. The reason for this application is that [[bit|binary values]] natively used in computing are [[base 2]] and not the [[base 10]] which is used for the [[SI prefix]]es. The NIST comments on this confusion: "Faced with this reality, the ''IEEE Standards Board'' decided that IEEE standards will use the conventional, internationally adopted, definitions of the SI prefixes", instead of kilo for 1024.<ref>[http://physics.nist.gov/cuu/Units/binary.html Definition of binary prefixes at NIST]</ref> Example: * One "[[kilobyte]]" (kB) is 1024 [[byte]]s in [[JEDEC memory standards|JEDEC-standard]], whereas the definition has shifted to, in most contexts, mean 1000 bytes (kB) in accordance with SI. To address this confusion, a new set of [[binary prefix]]es have been introduced which are based on powers of 2. In that system, 1024 bytes are called a [[kibibyte]] or 1 KiB. ==Exponentiation== When units occur in [[exponentiation]], such as in square and cubic forms, any multiplier prefix is considered part of the unit, and thus included in the exponentiation. * 1&nbsp;km² means one square kilometre or the area of a [[Square (geometry)|square]] that measures 1000&nbsp;m on each side or 10⁶&nbsp;m² (as opposed to 1000 square meters, which is the area of a square that measures 31.6&nbsp;m on each side). * 1&nbsp;km³ means one cubic kilometre or the volume of a [[cube]] that measures 1000&nbsp;m on each side or 10⁹&nbsp;m³ (as opposed to 1000 cubic meters, which is the volume of a cube that measures 10&nbsp;m on each side). ==See also== *[[milli-]] (inverse of kilo- prefix, denoting a factor of 1/1000) *[[kibi-]] (binary prefix, denoting a factor of 1024) ==References== {{reflist}} {{SI prefixes}} [[Category:SI prefixes]] [[Category:1000 (number)]] [[he:תחיליות במערכת היחידות הבינלאומית#קילו]]'