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.^[1][2][3] 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 1000^m 10^n Decimal English word Adoption[nb 1] Name Symbol Short scale Long scale yotta Y  1000^8  10^24 1000000000000000000000000  septillion  quadrillion 1991 zetta Z  1000^7  10^21 1000000000000000000000  sextillion  thousand trillion or trilliard 1991 exa E  1000^6  10^18 1000000000000000000  quintillion  trillion 1975 peta P  1000^5  10^15 1000000000000000  quadrillion  thousand billion or billiard 1975 tera T  1000^4  10^12 1000000000000  trillion  billion 1960 giga G  1000^3  10^9 1000000000  billion  thousand million or milliard 1960 mega M  1000^2  10^6 1000000             million 1960 (1873) kilo k  1000^1  10^3 1000             thousand 1960 (1795) hecto h  1000^2/3  10^2 100             hundred 1960 (1795) deca da  1000^1/3  10^1 10             ten 1960 (1795)  1000^0  10^0 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

1. 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.

See also

• Metric prefix
• Numeral prefix

References

1. Brewster, David (1830). The Edinburgh Encyclopædia 12. Edinburgh, UK: William Blackwood, John Waugh, John Murray, Baldwin & Cradock, J. M. Richardson. Retrieved 2015-10-09.
2. Brewster, David (1832). The Edinburgh Encyclopaedia 12 (1st American ed.). Joseph and Edward Parker. Retrieved 2015-10-09.
3. Dingler, Johann Gottfried (1823). Polytechnisches Journal (in German) 11. Stuttgart, Germany: J.W. Gotta'schen Buchhandlung. Retrieved 2015-10-09.