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Deca (International spelling as used by the International Bureau of Weights and Measures;[1] symbol: da) or deka (American spelling[2]) is a decimal unit prefix in the metric system denoting a factor of ten. The term is derived from the Greek déka (δέκα) meaning ten.

The prefix was a part of the original metric system in 1795. It is not in very common usage, although the decapascal is occasionally used by audiologists. The decanewton is also encountered occasionally, probably because it is an SI approximation of the kilogram-force. Its use is more common in Central Europe. In German, Polish, Czech, Slovak, and Hungarian, deka (or deko) is common, and used in self-standing form, always meaning decagram. A runway number typically indicates its magnetic azimuth in decadegrees.

Before the symbol as an SI prefix was standardized as da with the introduction of the International System of Units in 1960, various other symbols were more common, such as dk (e.g., UK and Austria), D (e.g., Germany, Eastern Europe), and Da. For syntactical reasons, the HP 48, 49, 50 series, as well as the HP 39gII and Prime calculators use the unit prefix D.[3][4][5]

Examples:

  • The blue whale is approximately 30 metres or 3 decametres in length.[6]
SI prefixes
PrefixBase 10 Decimal Adoption
[nb 1]
NameSymbol
quettaQ1030 10000000000000000000000000000002022[7]
ronnaR1027 1000000000000000000000000000
yottaY1024 10000000000000000000000001991
zettaZ1021 1000000000000000000000
exaE1018 10000000000000000001975[8]
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[7]
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. ↑ Decimal multiples and submultiples of SI units Archived 2019-03-30 at the Wayback Machine, 2006, SI Brochure: The International System of Units (SI), 8th edition
  2. ↑ Guide for the Use of the International System of Units (SI), 1995, NIST Special Publication 811
  3. ↑ HP 48G Series – User's Guide (UG) (8 ed.). Hewlett-Packard. December 1994 [1993]. HP 00048-90126, (00048-90104). Retrieved 2015-09-06.
  4. ↑ HP 50g graphing calculator user's guide (UG) (1 ed.). Hewlett-Packard. 2006-04-01. HP F2229AA-90006. Retrieved 2015-10-10.
  5. ↑ HP Prime Graphing Calculator User Guide (UG) (PDF) (1 ed.). Hewlett-Packard Development Company, L.P. October 2014. HP 788996-001. Archived from the original (PDF) on 2014-09-03. Retrieved 2015-10-13.
  6. ↑ "National Geographic TV Shows, Specials & Documentaries". Archived from the original on March 6, 2009.
  7. 1 2 "On the extension of the range of SI prefixes". 18 November 2022. Retrieved 5 February 2023.
  8. ↑ "Metric (SI) Prefixes". NIST.
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