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Deca- or deka-〔(''Guide for the Use of the International System of Units (SI)'' ), 1995, NIST Special Publication 811〕 (symbol da) is a decimal unit prefix in the metric system, denoting a factor of ten. The term is derived from the Greek ' (), 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 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" (f.e. in the UK and Austria), "D" (f.e. 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". * 1 decametre = 10 metres * 1 decalitre = 10 litres * 1 decare = 10 ares Examples: * The blue whale is approximately 30 meters or 3 decameters in length.〔http://channel.nationalgeographic.com/channel/content/kingdom-of-the-blue-whale-3302/blue-whale-facts/#/compare/length 〕 ==See also== *Metric prefix 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Deca-」の詳細全文を読む スポンサード リンク
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