Deca-

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

Deca (International spelling as used by the International Bureau of Weights and Measures; symbol: da) or deka (American spelling) 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.

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

Examples:

• The blue whale is approximately 30 metres or 3 decametres in length.

SI prefixes

Prefix		Base 10	Decimal	English word		Adoption	Etymology
Name	Symbol			Short scale	Long scale		Language	Source word
yotta	Y	1024	1000000000000000000000000	septillion	quadrillion	1991	Latin	eight
zetta	Z	1021	1000000000000000000000	sextillion	trilliard	1991	Latin	seven
exa	E	1018	1000000000000000000	quintillion	trillion	1975	Greek	six
peta	P	1015	1000000000000000	quadrillion	billiard	1975	Greek	five
tera	T	1012	1000000000000	trillion	billion	1960	Greek	four, monster
giga	G	109	1000000000	billion	milliard	1960	Greek	giant
mega	M	106	1000000	million		1873	Greek	great
kilo	k	103	1000	thousand		1795	Greek	thousand
hecto	h	102	100	hundred		1795	Greek	hundred
deca	da	101	10	ten		1795	Greek	ten
		100	1	one		–
deci	d	10−1	0.1	tenth		1795	Latin	ten
centi	c	10−2	0.01	hundredth		1795	Latin	hundred
milli	m	10−3	0.001	thousandth		1795	Latin	thousand
micro	μ	10−6	0.000001	millionth		1873	Greek	small
nano	n	10−9	0.000000001	billionth	milliardth	1960	Greek	dwarf
pico	p	10−12	0.000000000001	trillionth	billionth	1960	Spanish	peak, a little bit
femto	f	10−15	0.000000000000001	quadrillionth	billiardth	1964	Danish	fifteen, Fermi
atto	a	10−18	0.000000000000000001	quintillionth	trillionth	1964	Danish	eighteen
zepto	z	10−21	0.000000000000000000001	sextillionth	trilliardth	1991	Latin	seven
yocto	y	10−24	0.000000000000000000000001	septillionth	quadrillionth	1991	Latin	eight

See also

• Metric prefix

External links

• BIPM website