Deca-
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Deca (and dec), sometimes deka, is a common English-language numeral prefix derived from the Late Latin Template:Lang ("(set of) ten"), from Ancient Greek Template:Lang, from Template:Lang (déka, "ten").<ref>Template:Cite book</ref> It is used in many words.
It is also a decimal unit prefix in the International System of Units (SI) denoting a factor of ten, with symbol da and spelled "deca" internationallyTemplate:Efn (or "deka" in American spelling<ref name=SP811>Guide for the Use of the International System of Units (SI), 1995, NIST Special Publication 811</ref>).
SI
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.<ref name="HP48_UG">Template:Cite book</ref><ref name="HP50g_UG">Template:Cite book</ref><ref name="HP-Prime_UG">Template:Cite book</ref>
Examples:
- The blue whale is approximately 30 metres or 3 decametres in length.<ref>Template:Cite web</ref>
As an English prefix
The prefix is used in many words.
General
- Decathlon, a combined event in athletics consisting of ten track and field events.
- Decennial, ten-yearly or a celebration of ten years.
Mathematics
- Decimal based on the number ten.
- Decagon a plane figure with ten sides
- Decahedron a polyhedron with ten faces
Chemistry
- Decane, a hydrocarbon with 10 carbon atoms
Biology
- Decapoda, an order of crustaceans with ten feet
Religion
- The Decalogue, the Ten Commandments