Hecto-

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Hecto 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 hekaton, 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.

It is rarely used, except in 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 wine and milk) 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
hectare (ha, or 100 ares), in surveying, as a measure of land area equal to one square hectometre, 1 hm² = 10,000 m²

SI prefixes

Prefix		1000^m	10ⁿ	Decimal	English word		Adoption^{[nb 1]}
Name	Symbol	1000^m	10ⁿ	Decimal	Short scale	Long scale	Adoption^{[nb 1]}
yotta	Y	1000⁸	10²⁴	1000000000000000000000000	septillion	quadrillion	1991
zetta	Z	1000⁷	10²¹	1000000000000000000000	sextillion	thousand trillion or trilliard	1991
exa	E	1000⁶	10¹⁸	1000000000000000000	quintillion	trillion	1975
peta	P	1000⁵	10¹⁵	1000000000000000	quadrillion	thousand billion or billiard	1975
tera	T	1000⁴	10¹²	1000000000000	trillion	billion	1960
giga	G	1000³	10⁹	1000000000	billion	thousand million or milliard	1960
mega	M	1000²	10⁶	1000000	million		1960 (1873)
kilo	k	1000¹	10³	1000	thousand		1960 (1795)
hecto	h	1000^2/3	10²	100	hundred		1960 (1795)
deca	da	1000^1/3	10¹	10	ten		1960 (1795)
		1000⁰	10⁰	1	one		–
deci	d	1000^−1/3	10⁻¹	0.1	tenth		1960 (1795)
centi	c	1000^−2/3	10⁻²	0.01	hundredth		1960 (1795)
milli	m	1000⁻¹	10⁻³	0.001	thousandth		1960 (1795)
micro	μ	1000⁻²	10⁻⁶	0.000001	millionth		1960 (1873)
nano	n	1000⁻³	10⁻⁹	0.000000001	billionth	thousand millionth	1960
pico	p	1000⁻⁴	10⁻¹²	0.000000000001	trillionth	billionth	1960
femto	f	1000⁻⁵	10⁻¹⁵	0.000000000000001	quadrillionth	thousand billionth	1964
atto	a	1000⁻⁶	10⁻¹⁸	0.000000000000000001	quintillionth	trillionth	1964
zepto	z	1000⁻⁷	10⁻²¹	0.000000000000000000001	sextillionth	thousand trillionth	1991
yocto	y	1000⁻⁸	10⁻²⁴	0.000000000000000000000001	septillionth	quadrillionth	1991

↑ The metric system was introduced in 1795 with several metric prefixes, of which, however, only six were adopted as SI prefixes by the 11th CGPM conference in 1960, whereas myria (10⁴) as well as double and demi were not adopted. In 1873, micro and mega were recommended by the British Association for the Advancement of Science. The other dates relate to recognition by a resolution of the CGPM.

References

↑ Brewster, David (1832). The Edinburgh Encyclopaedia. 12 (1st American ed.). Joseph and Edward Parker. Retrieved 2015-10-09.
↑ Dingler, Johann Gottfried (1823). Polytechnisches Journal (in German). 11. Stuttgart, Germany: J.W. Gotta'schen Buchhandlung. Retrieved 2015-10-09.

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Hecto-

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References