Hecto
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hecto- (symbol h) is a SI prefix in the SI system of units denoting a factor of 102 (100).
Adopted in 1795, it comes from the Greek ἑκατόν hekaton, meaning hundred.
It is rarely used, except for certain specific applications:
- hectare, 100 ares, a very common measure of land area.
- hectopascal, in meteorology, for atmospheric pressure, the modern equivalent of the traditional millibar.
- hectolitre, in agriculture, for liquids (notably wine) and bulk commodities (e.g. grain).
- hectogram, in agronomy, for quantities of animal feed (hectogram/animal) and for measures of agricultural productivity (hectogram/hectare); also used in Italy, abbreviated as etto, for retail sale of cold cuts and meat.
- hectometre, in radio astronomy, occasionally used to indicate a radio band by wavelength
| 1000n | 10n | Prefix | Symbol | Short scale | Long scale | Decimal equivalent in SI writing style |
|---|---|---|---|---|---|---|
| 10008 | 1024 | yotta | Y | Septillion | Quadrillion | 1 000 000 000 000 000 000 000 000 |
| 10007 | 1021 | zetta | Z | Sextillion | Trilliard (thousand trillion) | 1 000 000 000 000 000 000 000 |
| 10006 | 1018 | exa | E | Quintillion | Trillion | 1 000 000 000 000 000 000 |
| 10005 | 1015 | peta | P | Quadrillion | Billiard (thousand billion) | 1 000 000 000 000 000 |
| 10004 | 1012 | tera | T | Trillion | Billion | 1 000 000 000 000 |
| 10003 | 109 | giga | G | Billion | Milliard (thousand million) | 1 000 000 000 |
| 10002 | 106 | mega | M | Million | 1 000 000 | |
| 10001 | 103 | kilo | k | Thousand | 1 000 | |
| 10002/3 | 102 | hecto | h | Hundred | 100 | |
| 10001/3 | 101 | deca, deka | da | Ten | 10 | |
| 10000 | 100 | (none) | (none) | One | 1 | |
| 1000−1/3 | 10−1 | deci | d | Tenth | 0.1 | |
| 1000−2/3 | 10−2 | centi | c | Hundredth | 0.01 | |
| 1000−1 | 10−3 | milli | m | Thousandth | 0.001 | |
| 1000−2 | 10−6 | micro | µ (u) | Millionth | 0.000 001 | |
| 1000−3 | 10−9 | nano | n | Billionth | Milliardth | 0.000 000 001 |
| 1000−4 | 10−12 | pico | p | Trillionth | Billionth | 0.000 000 000 001 |
| 1000−5 | 10−15 | femto | f | Quadrillionth | Billiardth | 0.000 000 000 000 001 |
| 1000−6 | 10−18 | atto | a | Quintillionth | Trillionth | 0.000 000 000 000 000 001 |
| 1000−7 | 10−21 | zepto | z | Sextillionth | Trilliardth | 0.000 000 000 000 000 000 001 |
| 1000−8 | 10−24 | yocto | y | Septillionth | Quadrillionth | 0.000 000 000 000 000 000 000 001 |
