peta-


This article describes the SI prefix. For other meanings, see Peta.
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In physics and mathematics, peta- (symbol: P) is a prefix in the SI (system of units) denoting 1015, or 1,000,000,000,000,000. For example:

1 petametre = 1015 metres
1 petasecond = 1015 seconds

Adopted in 1975, it comes from the Greek πέντε, meaning five, because it is equal to 10005. It is based on the model of tera- (from Greek τέρας = 'immense', 'tremendous', but looking like tetra- from the Greek for "four" with a letter missing), and so peta-, coming from penta-, omits the third letter, n.

Examples:

In computer science peta- can sometimes mean 1 125 899 906 842 624 (10245 or 250), instead of 1 000 000 000 000 000, especially when used to prefix the byte, giving a petabyte. To resolve this ambiguity, the term pebibyte has been suggested to mean 250 bytes.

SI prefixes
1000m 10n Prefix Symbol Since[1] Short scale Long scale Decimal
10008 1024 yotta Y 1991 Septillion Quadrillion 1000000000000000000000000
10007 1021 zetta Z 1991 Sextillion Trilliard 1000000000000000000000
10006 1018 exa E 1975 Quintillion Trillion 1000000000000000000
10005 1015 peta P 1975 Quadrillion Billiard 1000000000000000
10004 1012 tera T 1960 Trillion Billion 1000000000000
10003 109 giga G 1960 Billion Milliard 1000000000
10002 106 mega M 1960 Million 1 000 000
10001 103 kilo k 1795 Thousand 1000
10002⁄3 102 hecto h 1795 Hundred 100
10001⁄3 101 deca da 1795 Ten 10
10000 100 (none) (none) NA One 1
1000−1⁄3 10−1 deci d 1795 Tenth 0.1
1000−2⁄3 10−2 centi c 1795 Hundredth 0.01
1000−1 10−3 milli m 1795 Thousandth 0.001
1000−2 10−6 micro µ 1960[2] Millionth 0.000001
1000−3 10−9 nano n 1960 Billionth Milliardth 0.000000001
1000−4 10−12 pico p 1960 Trillionth Billionth 0.000000000001
1000−5 10−15 femto f 1964 Quadrillionth Billiardth 0.000000000000001
1000−6 10−18 atto a 1964 Quintillionth Trillionth 0.000000000000000001
1000−7 10−21 zepto z 1991 Sextillionth Trilliardth 0.000000000000000000001
1000−8 10−24 yocto y 1991 Septillionth Quadrillionth 0.000000000000000000000001
  1. The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM.
  2. The 1948 recognition of the micron by the CGPM was abrogated in 1967.

See also

External links

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