Atto-
Atto (symbol a) is a unit prefix in the metric system denoting a factor of 10−18 or 0.000000000000000001.
Look up atto- in Wiktionary, the free dictionary. |
The unit multiple was adopted at the 12th General Conference on Weights and Measures (CGPM) in Resolution 8.[1] It is derived from the Danish word atten, meaning "eighteen".
Examples of its use:
- Weight of the HIV-1 virus is about 1×10−18 kg or 1×10−15 g, which can be written as 1 fg or 1000 ag.
- More examples available.
Prefix | Base 10 | Decimal | English word | Adoption[nb 1] | |||
---|---|---|---|---|---|---|---|
Name | Symbol | Short scale | Long scale | ||||
yotta- | Y- | 1024 | 1000000000000000000000000 | septillion | quadrillion | 1991 | |
zetta- | Z- | 1021 | 1000000000000000000000 | sextillion | trilliard | 1991 | |
exa- | E- | 1018 | 1000000000000000000 | quintillion | trillion | 1975 | |
peta- | P- | 1015 | 1000000000000000 | quadrillion | billiard | 1975 | |
tera- | T- | 1012 | 1000000000000 | trillion | billion | 1960 | |
giga- | G- | 109 | 1000000000 | billion | milliard | 1960 | |
mega- | M- | 106 | 1000000 | million | 1873 | ||
kilo- | k- | 103 | 1000 | thousand | 1795 | ||
hecto- | h- | 102 | 100 | hundred | 1795 | ||
deca- | da- | 101 | 10 | ten | 1795 | ||
100 | 1 | one | – | ||||
deci- | d- | 10−1 | 0.1 | tenth | 1795 | ||
centi- | c- | 10−2 | 0.01 | hundredth | 1795 | ||
milli- | m- | 10−3 | 0.001 | thousandth | 1795 | ||
micro- | μ- | 10−6 | 0.000001 | millionth | 1873 | ||
nano- | n- | 10−9 | 0.000000001 | billionth | milliardth | 1960 | |
pico- | p- | 10−12 | 0.000000000001 | trillionth | billionth | 1960 | |
femto- | f- | 10−15 | 0.000000000000001 | quadrillionth | billiardth | 1964 | |
atto- | a- | 10−18 | 0.000000000000000001 | quintillionth | trillionth | 1964 | |
zepto- | z- | 10−21 | 0.000000000000000000001 | sextillionth | trilliardth | 1991 | |
yocto- | y- | 10−24 | 0.000000000000000000000001 | septillionth | quadrillionth | 1991 | |
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References
- International Bureau of Weights and Measures (2006), The International System of Units (SI) (PDF) (8th ed.), ISBN 92-822-2213-6, archived (PDF) from the original on 2017-08-14
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