Deca-

This article is about the SI prefix. For other uses, see Deca.

Deca- or deka- (symbol da) is a prefix in the metric system, also a numerical prefix, denoting a factor of ten. The term is derived from the Greek δέκα meaning "ten". Its symbol is the only SI prefix that uses more than one character.

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, Czech, Slovak and Hungarian, deca is common (and always means decagram).

Before the symbol was standardized as da with the introduction of the International System of Units in 1960, various other symbols were more common, such as "dk", "D", and "Da".

• 1 decametre = 10 metres
• 1 decalitre = 10 litres
• 1 decare = 10 ares

SI prefixes

Prefix	Symbol	1000m	10n	Decimal	Short scale	Long scale	Since
yotta	Y	10008	1024	1000000000000000000000000	Septillion	Quadrillion	1991
zetta	Z	10007	1021	1000000000000000000000	Sextillion	Trilliard	1991
exa	E	10006	1018	1000000000000000000	Quintillion	Trillion	1975
peta	P	10005	1015	1000000000000000	Quadrillion	Billiard	1975
tera	T	10004	1012	1000000000000	Trillion	Billion	1960
giga	G	10003	109	1000000000	Billion	Milliard	1960
mega	M	10002	106	1000000	Million		1960
kilo	k	10001	103	1000	Thousand		1795
hecto	h	10002/3	102	100	Hundred		1795
deca	da	10001/3	101	10	Ten		1795
		10000	100	1	One		–
deci	d	1000−1/3	10−1	0.1	Tenth		1795
centi	c	1000−2/3	10−2	0.01	Hundredth		1795
milli	m	1000−1	10−3	0.001	Thousandth		1795
micro	μ	1000−2	10−6	0.000001	Millionth		1960
nano	n	1000−3	10−9	0.000000001	Billionth	Milliardth	1960
pico	p	1000−4	10−12	0.000000000001	Trillionth	Billionth	1960
femto	f	1000−5	10−15	0.000000000000001	Quadrillionth	Billiardth	1964
atto	a	1000−6	10−18	0.000000000000000001	Quintillionth	Trillionth	1964
zepto	z	1000−7	10−21	0.000000000000000000001	Sextillionth	Trilliardth	1991
yocto	y	1000−8	10−24	0.000000000000000000000001	Septillionth	Quadrillionth	1991

See also

• Decamer, a thing composed of ten sub-units

External links

• BIPM website