Hecto-

Hecto (symbol: h) is a decimal unit prefix in the metric system denoting a factor of one hundred. It was adopted as a multiplier in 1795, and comes from the Greek ἑκατόν hekatón, meaning "hundred". In 19th century English it was sometimes spelled "hecato", in line with a puristic opinion by Thomas Young.[1][2] Its unit symbol as an SI prefix in the International System of Units (SI) is the lower case letter h.

The prefix is rarely used in general, but has certain specific applications:

* hectopascal (hPa), in meteorology, for atmospheric pressure, the modern equivalent of the traditional millibar.
* hectolitre (hl or hL), in agriculture, for liquids (notably milk and alcoholic beverages) and bulk commodities (e.g., grain).
* hectogram (hg), in agronomy, for quantities of animal feed (hectogram/animal) and for measures of agricultural productivity (hectogram/hectare); also used in Italy abbreviated as etto, and in Canada, New Zealand and Sweden simply as 100 g, for retail sale of cold cuts and meat.
* hectometre (hm), in radio astronomy, occasionally used to indicate a radio band by wavelength
* In surveying, a square hectometre is called a hectare (ha, or 100 ares = 1 hm2 = 10,000 m2).

SI prefixesv * d * e

Prefix  | Base 10  | Decimal | English word  | Adoption[nb 1]

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|
|
|

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

1. ↑ Prefixes adopted before 1960 already existed before SI. 1873 was the introduction of the CGS system.

## See also

* Metric prefix
* Numeral prefix

## References

1. ↑ Brewster, David (1832). The Edinburgh Encyclopaedia. 12 (1st American ed.). Joseph and Edward Parker. https://books.google.com/books?id=17RGAQAAIAAJ&pg=PA572. Retrieved 2015-10-09.
2. ↑ Dingler, Johann Gottfried (1823) (in de). Polytechnisches Journal. 11. Stuttgart, Germany: J.W. Gotta'schen Buchhandlung. https://books.google.com/books?id=wF3zAAAAMAAJ&pg=PA500. Retrieved 2015-10-09.

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