Deca-

Deca- or deka- (symbol da) is a decimal unit prefix in the metric system, denoting a factor of ten. The term is derived from the Greek deka (), 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 (deka, deko), Czech, Slovak and Hungarian, deca is common (and used as a word on its own always means decagram). A runway number typically indicates its heading 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. in the UK and Austria), "D" (e.g. in Germany), 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".

Examples:

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