pre. In the International System of Units and other metric systems of units, multiplying the unit to which it is attached by 100. Symbol: h
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 , 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 , 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), in surveying, as a measure of land area equal to 10,000 m or one square hectometre (100 ares)