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'{{Short description|Decimal unit prefix in the metric system}} {{Other uses|Kilo (disambiguation)}} {{Wiktionary|kilo-}} '''Kilo''' is a [[decimal prefix|decimal]] [[metric prefix|unit prefix]] in the [[metric system]] denoting multiplication by one [[thousand]] (10³). It is used in the [[International System of Units]], where it has the 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". In 19th century English it was sometimes spelled chilio, in line with a [[Linguistic purism|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|access-date=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=de|location=Stuttgart, Germany|url=https://books.google.com/books?id=wF3zAAAAMAAJ&pg=PA500|access-date=2015-10-09}}</ref> As an opponent of suggestions to introduce the metric system in Britain, he qualified the nomenclature adopted in France as barbarous. == Examples == * one [[kilogram]] (kg) is 1000 [[gram]]s * one [[kilometre]] (km) is 1000 [[metre]]s * one [[kilojoule]] (kJ) is 1000 [[joule]]s * one kilolitre (kL) is 1000 [[litre]]s * one kilobaud (kBd) is 1000 [[baud]] * one kilohertz (kHz) is 1000 [[hertz]] * one [[kilobit]] (kb) is 1000 [[bit]]s * one [[kilobyte]] (kB) is 1000 [[byte]]s * one kiloohm is (kΩ) is 1000 [[ohm]]s * one [[kilosecond]] (ks) is 1000 [[Second|seconds]] *one [[kilotonne]] (kt) is 1000 [[Tonne|tonnes]] By extension, currencies are also sometimes preceded by the prefix kilo-: * one kiloeuro (k€) is 1000 [[euros]] * one kilodollar (k$) is 1000 [[dollars]] ==kilobyte== For the kilobyte, a second definition has been in common use in some fields of [[computer science]] and information technology. It uses ''kilobyte'' to mean 2¹⁰ bytes (= 1024 bytes), because of the [[Mathematical coincidence#Concerning base 2|mathematical coincidence]] that 2¹⁰ is approximately 10³. The reason for this application is that digital hardware and architectures natively use [[base 2]] exponentiation, and not [[base 10|decimal]] systems. [[JEDEC memory standards]] still permit this definition, but acknowledge the correct SI usage. NIST comments on the confusion caused by these contrasting definitions: "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> To address this conflict, a new set of [[binary prefix]]es has been introduced, which is based on powers of 2. Therefore, 1024 bytes are defined as one [[kibibyte]] (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) * [[RKM code]] ==References== {{reflist}} {{SI prefixes (infobox)}} [[Category:SI prefixes]] [[Category:1000 (number)]] [[he:תחיליות במערכת היחידות הבינלאומית#קילו]]'