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mega (symbol M) is an SI prefix in the SI system of units denoting a factor of 10⁶, 1,000,000 (one million).

For example, 1 MW (megawatt) = 1,000,000 watts = 1,000 kilowatts.

Confirmed in 1960, it comes from the Greek μέγας, meaning great.^[1]

Contents 1 Other common examples of usage 2 Exponentiation 3 Computing 4 See also 5 References 6 External links

[edit] Other common examples of usage

• megapixel - 1 million pixels in a digital camera
• one megaton [of TNT] (a unit often used in measuring the explosive power of nuclear weapons) is 1,000,000 tons of TNT.
• megahertz—frequency of electromagnetic radiation for radio and television broadcasting, GSM, etc. 1 MHz = 1,000,000 Hz.
• megadeath - one million deaths caused by nuclear war

[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 Mm² means one square megametre or the size of a square of 1,000,000 m by 1,000,000 m or 10¹² m², and not 1,000,000 square metres (10⁶ m²).
• 1 Mm³ means one cubic megametre or the size of a cube of 1,000,000 m by 1,000,000 m by 1,000,000 m or 10¹⁸ m³, and not 1,000,000 cubic metres (10⁶ m³)

[edit] Computing

In computing, mega can sometimes denote 1,048,576 (2²⁰) of information units (example: a megabyte, a megaword), but can denote 1,000,000 (10⁶) of other quantities, for example, transfer rates: 1 megabit/s = 1,000,000 bit/s.

The prefix mebi has been suggested as a prefix for 2²⁰ to avoid ambiguity.

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.

[edit] See also

• SI prefix
• Binary prefix
• Mebibyte
• Orders of magnitude

[edit] References

1. ^ "[http://dictionary.oed.com/cgi/entry/00304790 mega-]". Oxford English Dictionary. Oxford University Press. 2nd ed. 1989.

[edit] External links

• BIPM website