Deca-

For other uses, see Deca.

Deca (and dec), sometimes deka, is a common English-language numeral prefix derived from the Late Latin decas ("(set of) ten"), from Ancient Greek δεκάς (dekás), from δέκα (déka, "ten").^[1] 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" internationally^[a] (or "deka" in American spelling^[3]).

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.^[4][5][6]

• 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.^[7]

SI prefixes

• v
• t
• e

Prefix		Base 10	Decimal	Adoption [nb 1]
Name	Symbol
quetta	Q	1030	1000000000000000000000000000000	2022[8]
ronna	R	1027	1000000000000000000000000000
yotta	Y	1024	1000000000000000000000000	1991
zetta	Z	1021	1000000000000000000000
exa	E	1018	1000000000000000000	1975[9]
peta	P	1015	1000000000000000
tera	T	1012	1000000000000	1960
giga	G	109	1000000000
mega	M	106	1000000	1873
kilo	k	103	1000	1795
hecto	h	102	100
deca	da	101	10
—	—	100	1	—
deci	d	10−1	0.1	1795
centi	c	10−2	0.01
milli	m	10−3	0.001
micro	μ	10−6	0.000001	1873
nano	n	10−9	0.000000001	1960
pico	p	10−12	0.000000000001
femto	f	10−15	0.000000000000001	1964
atto	a	10−18	0.000000000000000001
zepto	z	10−21	0.000000000000000000001	1991
yocto	y	10−24	0.000000000000000000000001
ronto	r	10−27	0.000000000000000000000000001	2022[8]
quecto	q	10−30	0.000000000000000000000000000001
Notes Prefixes adopted before 1960 already existed before SI. The introduction of the CGS system was in 1873.

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

See also

• Metric prefix

Notes

1. As used by the International Bureau of Weights and Measures.^[2]