Atto Atto

Atto - Definition and Overview

Atto- (symbol a) is an SI prefix to a unit and means that it is 10-18 times this unit. Examples are one attosecond or one attometre (U.S. spelling attometer).

Adopted in 1964, it comes from the Danish atten, meaning eighteen.

SI prefixes
10n Prefix Symbol Short scale Long scale Name Decimal Equivalent
1024 yotta Y Septillion Quadrillion 1 000 000 000 000 000 000 000 000
1021 zetta Z Sextillion Trilliard (thousand trillion) 1 000 000 000 000 000 000 000
1018 exa E Quintillion Trillion 1 000 000 000 000 000 000
1015 peta P Quadrillion Billiard (thousand billion) 1 000 000 000 000 000
1012 tera T Trillion Billion 1 000 000 000 000
109 giga G Billion Milliard (thousand million) 1 000 000 000
106 mega M Million 1 000 000
103 kilo k Thousand 1 000
102 hecto h Hundred 100
101 deca, deka da Ten 10
10−1 deci d Tenth 0.1
10−2 centi c Hundredth 0.01
10−3 milli m Thousandth 0.001
10−6 micro µ Millionth 0.000 001
10−9 nano n Billionth Milliardth 0.000 000 001
10−12 pico p Trillionth Billionth 0.000 000 000 001
10−15 femto f Quadrillionth Billiardth 0.000 000 000 000 001
10−18 atto a Quintillionth Trillionth 0.000 000 000 000 000 001
10−21 zepto z Sextillionth Trilliardth 0.000 000 000 000 000 000 001
10−24 yocto y Septillionth Quadrillionth 0.000 000 000 000 000 000 000 001
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See also

Example Usage of Atto
peko_atto: きまぐれ: おにぎり　と　おむすび http://peko-Atto.at.webry.info/200911/article_33.html
princeofmyword: @Amalianda Ho tante idee per la testa,tutte diversissime...vorrei vivere tante vite e metterle in Atto tutte.Mi se (cont) http://tl.gd/1183o
sharpTag: @KeiraVDW "ci sono più cose tra cielo e terra Orazio, di quante ne sogni la tua filosofia" Amleto, Atto I
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