Kilo-

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search

Kilo is a decimal 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 unit symbol k, in lower case.

The prefix kilo is derived from the Greek word χίλιοι (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 chilio, in line with a puristic opinion by Thomas Young[1][2]

Examples[edit]

By extension, currencies are also sometimes preceded by the prefix kilo-:

  • one kiloeuro (k€) is 1000 euros
  • one kilodollar (k$) is 1000 dollars

kilobyte[edit]

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 that 210 is approximately 103. The reason for this application is that digital hardware and architectures natively use base 2 exponentiation, and not 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.[3] To address this conflict, a new set of binary prefixes has been introduced, which is based on powers of 2. Therefore, 1024 bytes are defined as one kibibyte (1 KiB).

Exponentiation[edit]

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 km2 means one square kilometre or the area of a square that measures 1000 m on each side or 106 m2 (as opposed to 1000 square meters, which is the area of a square that measures 31.6 m on each side).
  • 1 km3 means one cubic kilometre or the volume of a cube that measures 1000 m on each side or 109 m3 (as opposed to 1000 cubic meters, which is the volume of a cube that measures 10 m on each side).

See also[edit]

  • milli- (inverse of kilo- prefix, denoting a factor of 1/1000)
  • kibi- (binary prefix, denoting a factor of 1024)
  • RKM code

References[edit]

  1. ^ Brewster, David (1832). The Edinburgh Encyclopaedia. 12 (1st American ed.). Joseph and Edward Parker. Retrieved 2015-10-09.
  2. ^ Dingler, Johann Gottfried (1823). Polytechnisches Journal (in German). 11. Stuttgart, Germany: J.W. Gotta'schen Buchhandlung. Retrieved 2015-10-09.
  3. ^ Definition of binary prefixes at NIST
Prefix power of 1000 power of 10 Base 10 English word Adoption[nb 1]
Name Symbol Short scale Long scale
yocto y  1000⁻⁸  10⁻²⁴  0.000000000000000000000001  septillionth  quadrillionth 1991
zepto z  1000⁻⁷  10⁻²¹ 0.000000000000000000001000  sextillionth  trilliardth 1991
atto a  1000⁻⁶  10⁻¹⁸ 0.000000000000000001000000  quintillionth  trillionth 1964
femto f  1000⁻⁵  10⁻¹⁵ 0.000000000000001000000000  quadrillionth  billiardth 1964
pico p  1000⁻⁴  10⁻¹² 0.000000000001000000000000  trillionth  billionth 1960
nano n  1000⁻³  10⁻⁹ 0.000000001000000000000000  billionth  milliardth 1960
micro μ  1000⁻²  10⁻⁶ 0.000001000000000000000000  millionth 1873
milli m  1000⁻¹  10⁻³ 0.001000000000000000000000  thousandth 1795
centi c  1000⁻2⁄3   10⁻² 0.010000000000000000000000  hundredth 1795
deci d  1000⁻1⁄3  10⁻¹ 0.100000000000000000000000  tenth 1795
 1000⁰  10⁰ 1.000000000000000000000000  one Unknown
deca da  10001⁄3  10¹ 10.000000000000000000000000  ten 1795
hecto h  10002⁄3  10² 100.000000000000000000000000  hundred 1795
kilo k  1000¹  10³ 1000.000000000000000000000000  thousand 1795
mega M  1000²  10⁶ 1000000.000000000000000000000000  million 1873
giga G  1000³  10⁹ 1000000000.000000000000000000000000  billion  milliard 1960
tera T  1000⁴  10¹² 1000000000000.000000000000000000000000  trillion  billion 1960
peta P  1000⁵  10¹⁵ 1000000000000000.000000000000000000000000  quadrillion  billiard 1975
exa E  1000⁶  10¹⁸ 1000000000000000000.000000000000000000000000  quintillion  trillion 1975
zetta Z  1000⁷  10²¹ 1000000000000000000000.000000000000000000000000  sextillion  trilliard 1991
yotta Y  1000⁸  10²⁴ 1000000000000000000000000.000000000000000000000000  septillion  quadrillion 1991
  1. ^ Prefixes adopted before 1960 already existed before SI. 1873 was the introduction of the CGS system.