femto-
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This article describes the SI prefix. For the manga character, see Berserk (manga).
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femto (symbol f) is a prefix in the International System of Units denoting a factor of 10−15 or 0.000000000000001. Adopted by the 11th Conférence Générale des Poids et Mesures,[1] it was added in 1964 to the SI.[2] It is derived from the Danish word femten, meaning "fifteen".
Example of use:
- a proton has a diameter of about 1.6 to 1.7 femtometres.
Note that the femtometre shares the same unit symbol (fm) with the older non-SI unit fermi, to which it is equivalent. The fermi, named in honour of Enrico Fermi, is often encountered in nuclear physics.[citation needed]
| 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 |
