Micro-: Definition from Answers.com

This article describes the SI prefix. For other meanings, see Micro.

Look up micro- in Wiktionary, the free dictionary.

The term micro (µ) is a prefix in the SI and other systems of units denoting a factor of 10⁻⁶ (one millionth).^[1] Confirmed in 1960, the prefix comes from the Greek μικρός (mikrós), meaning "small".

The symbol for it is the micro sign µ, the Greek letter mu (μ). For historical reasons, these are two different characters in Unicode, which appear slightly different in some fonts. The micro sign is encoded in the "Latin-1 Supplement" range identical to ISO/IEC 8859-1 (since 1985), at U+00B5 (Unicode 1.0, 1991). The Greek letter is encoded in the Greek range at U+03BC.

In circumstances where only the Latin alphabet is available, the prefix can be represented using the letter u as in "um" for µm, or "uF" for µF.^[2] In some contexts, such as pharmacy, microgram is often written mcg, which is nonstandard.

SI prefixes
1000^m	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		1 000 000
1000¹	10³	kilo	k	1795	Thousand		1000
1000^²⁄₃	10²	hecto	h	1795	Hundred		100
1000^¹⁄₃	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.

References

^ International Bureau of Weights and Measures (2006), The International System of Units (SI) (8th ed.), ISBN 92-822-2213-6, http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf
^ ISO 2955, Table 2.

Micro Duvet	Micro Centre
Micro Thong	Sandisk Micro

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Micro-

References

See also