Kilo-


Kilo is a unit prefix in the metric system of measurement, denoting multiplication by one thousand. The International System of Units reserves the lowercase symbol k.
Kilo is derived from the Greek word χίλιοι, meaning "thousand".
In 19th century English the prefix was sometimes spelled chilio, in line with a puristic opinion by Thomas Young. As an opponent of suggestions to introduce the metric system in Britain, he qualified the nomenclature adopted in France as barbarous.

Examples

By extension, currencies are sometimes also preceded by the prefix:
  • one kiloeuro is 1000 euros
  • one kilodollar is 1000 dollars

kilobyte

For multiples of the byte in some fields of computer science and information technology, another definition has been in common use, in which the kilobyte measures 1024 bytes, because 210 is approximately 103. The reason for this application is that digital hardware natively use base 2 exponentiation.
The National Institute of Standards and Technology 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." A new set of binary prefixes, based on powers of 2, was introduced by the International Electrotechnical Commission, which defines 1024 bytes as one kibibyte.

Exponentiation

When units occur in exponentiation, such as in square and cubic forms, any multiplier prefix is part of the unit, and thus included in the exponentiation.