Mega-

Mega- (symbol M) is an prefix in the metric system denoting a factor of million (10⁶ or 1000000). Confirmed in 1960, it comes from the Greek μέγας, meaning great.^[1]

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

Other common examples of usage

megapixel - 1 million pixels in a digital camera
one megatonne (of TNT) (a unit often used in measuring the explosive power of nuclear weapons) is the approximate energy released on igniting one million tonnes of TNT.
megahertz — frequency of electromagnetic radiation for radio and television broadcasting, GSM, etc. 1 MHz = 1,000,000 Hz.

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)

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
Prefix	Symbol	1000^m	10ⁿ	Decimal	Short scale	Long scale	Scientific notation	Since^{[n 1]}
yotta	Y	1000⁸	10²⁴	1000000000000000000000000	Septillion	Quadrillion	1E24	1991
zetta	Z	1000⁷	10²¹	1000000000000000000000	Sextillion	Trilliard	1E21	1991
exa	E	1000⁶	10¹⁸	1000000000000000000	Quintillion	Trillion	1E18	1975
peta	P	1000⁵	10¹⁵	1000000000000000	Quadrillion	Billiard	1E15	1975
tera	T	1000⁴	10¹²	1000000000000	Trillion	Billion	1E12	1960
giga	G	1000³	10⁹	1000000000	Billion	Milliard	1E9	1960
mega	M	1000²	10⁶	1000000	Million		1E6	1960
kilo	k	1000¹	10³	1000	Thousand		1E3	1795
hecto	h	1000^2/3	10²	100	Hundred		1E2	1795
deca	da	1000^1/3	10¹	10	Ten		1E1	1795
		1000⁰	10⁰	1	One		–	–
deci	d	1000^−1/3	10⁻¹	0.1	Tenth		1E-1	1795
centi	c	1000^−2/3	10⁻²	0.01	Hundredth		1E-2	1795
milli	m	1000⁻¹	10⁻³	0.001	Thousandth		1E-3	1795
micro	μ	1000⁻²	10⁻⁶	0.000001	Millionth		1E-6	1960
nano	n	1000⁻³	10⁻⁹	0.000000001	Billionth	Milliardth	1E-9	1960
pico	p	1000⁻⁴	10⁻¹²	0.000000000001	Trillionth	Billionth	1E-12	1960
femto	f	1000⁻⁵	10⁻¹⁵	0.000000000000001	Quadrillionth	Billiardth	1E-15	1964
atto	a	1000⁻⁶	10⁻¹⁸	0.000000000000000001	Quintillionth	Trillionth	1E-18	1964
zepto	z	1000⁻⁷	10⁻²¹	0.000000000000000000001	Sextillionth	Trilliardth	1E-21	1991
yocto	y	1000⁻⁸	10⁻²⁴	0.000000000000000000000001	Septillionth	Quadrillionth	1E-24	1991
^ The metric system was introduced in 1795 with six prefixes. The other dates relate to recognition by a resolution of the CGPM.

References

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

External links

BIPM website