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Look up kilo- in Wiktionary, the free dictionary.

Kilo (symbol: k) is a unit prefix in the International System of Units (SI) denoting 10³ or 1000. For example:

• one kilogram is 1000 grams
• one kilometre is 1000 metres
• one kilojoule is 1000 joules
• one kilobyte is equal to either 1000 bytes or, according to traditional use in some fields of computer science, 1024 (2¹⁰) bytes. The latter meaning is most often used when discussing computer memory and storage sizes. This usage has been officially replaced in the standardization bodies by the definition of binary prefixes.

The kilo prefix is derived from the Greek word χίλιοι ("chilioi"), meaning thousand. It was originally adopted by Antoine Lavoisier and his group in 1795, and introduced into the metric system in France with its establishment in 1799. The General Conference on Weights and Measures was formed in 1875.

[edit] Exponentiation

When units occur in exponentiation, such as in square and cubic forms, any size prefix is considered part of the unit, and thus included in the exponentiation.

• 1 km² means one square kilometre or the size of a square of 1,000 m by 1,000 m or 10⁶ m².
• 1 km³ means one cubic kilometre or the size of a cube of 1,000 m by 1,000 m by 1,000 m or 10⁹ m³.

SI prefixes

1000m	10n	Prefix	Symbol	Since[1]	Short scale	Long scale	Decimal
10008	1024	yotta	Y	1991	Septillion	Quadrillion	1000000000000000000000000
10007	1021	zetta	Z	1991	Sextillion	Trilliard	1000000000000000000000
10006	1018	exa	E	1975	Quintillion	Trillion	1000000000000000000
10005	1015	peta	P	1975	Quadrillion	Billiard	1000000000000000
10004	1012	tera	T	1960	Trillion	Billion	1000000000000
10003	109	giga	G	1960	Billion	Milliard	1000000000
10002	106	mega	M	1960	Million		1000000
10001	103	kilo	k	1795	Thousand		1000
10002⁄3	102	hecto	h	1795	Hundred		100
10001⁄3	101	deca	da	1795	Ten		10
10000	100	(none)	(none)	NA	One		1
1000−1⁄3	10−1	deci	d	1795	Tenth		0.1
1000−2⁄3	10−2	centi	c	1795	Hundredth		0.01
1000−1	10−3	milli	m	1795	Thousandth		0.001
1000−2	10−6	micro	µ	1960[2]	Millionth		0.000001
1000−3	10−9	nano	n	1960	Billionth	Milliardth	0.000000001
1000−4	10−12	pico	p	1960	Trillionth	Billionth	0.000000000001
1000−5	10−15	femto	f	1964	Quadrillionth	Billiardth	0.000000000000001
1000−6	10−18	atto	a	1964	Quintillionth	Trillionth	0.000000000000000001
1000−7	10−21	zepto	z	1991	Sextillionth	Trilliardth	0.000000000000000000001
1000−8	10−24	yocto	y	1991	Septillionth	Quadrillionth	0.000000000000000000000001
The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM. The 1948 recognition of the micron by the CGPM was abrogated in 1967.