exa-


This article is about the SI prefix. For the X Window System acceleration architecture, see EXA.
Sister project Look up exa- in Wiktionary, the free dictionary.

exa (symbol E) is a prefix in the SI system of units denoting 1018 or 1 000 000 000 000 000 000.

Adopted in 1975, it comes from the Greek ἕξ, meaning six (like hexa), because it is equal to 10006.

Examples:

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

References

External links

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