Hecto-

Hecto or hecta 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". Based on a proposal by Thomas Young, the prefix was often alternatively spelled hecato- in early 19th century sources. 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 and New Zealand 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), in surveying, as a measure of land area equal to 10,000 m² or one square hectometre (100 ares)

SI prefixes

Prefix 1000m 10n Decimal English word Adoption Name Symbol Short scale Long scale 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  10002/3  102 100             hundred 1960 (1795) deca da  10001/3  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

See also

• Metric prefix
• Numeral prefix