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:

PrefixBase 10 Decimal Adoption
[nb 1]
NameSymbol
quettaQ1030 10000000000000000000000000000002022[3]
ronnaR1027 1000000000000000000000000000
yottaY1024 10000000000000000000000001991
zettaZ1021 1000000000000000000000
exaE1018 10000000000000000001975[4]
petaP1015 1000000000000000
teraT1012 10000000000001960
gigaG109 1000000000
megaM106 10000001873
kilok103 10001795
hectoh102100
decada10110
1001
decid10−1 0.11795
centic10−2 0.01
millim10−3 0.001
microμ10−6 0.0000011873
nanon10−9 0.0000000011960
picop10−12 0.000000000001
femtof10−15 0.0000000000000011964
attoa10−18 0.000000000000000001
zeptoz10−21 0.0000000000000000000011991
yoctoy10−24 0.000000000000000000000001
rontor10−27 0.0000000000000000000000000012022[3]
quectoq10−30 0.000000000000000000000000000001
Notes
  1. Prefixes adopted before 1960 already existed before SI. The introduction of the CGS system was in 1873.

See also

References

  1. Brewster, David (1832). The Edinburgh Encyclopaedia. Vol. 12 (1st American ed.). Joseph and Edward Parker. Retrieved 2015-10-09.
  2. Dingler, Johann Gottfried (1823). Polytechnisches Journal (in German). Vol. 11. Stuttgart, Germany: J.W. Gotta'schen Buchhandlung. Retrieved 2015-10-09.
  3. 1 2 "On the extension of the range of SI prefixes". 18 November 2022. Retrieved 5 February 2023.
  4. "Metric (SI) Prefixes". NIST.
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