Giga

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For the Baroque dance, see gigue.

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giga- (symbol: G) is a prefix in the SI system of units denoting 10⁹, or 1,000,000,000 (1 billion).

Confirmed in 1960, it comes from the Greek γίγας, meaning giant.

When referring to computing information units, such as gigabit or gigabyte, giga- can sometimes mean 1,073,741,824 (2³⁰), but can also denote 1,000,000,000 (10⁹). The exact definition being used is ambiguous, and must be determined from context. The binary prefix gibi- has been standardized for 2³⁰, while reserving giga- exclusively for 10⁹, to resolve this ambiguity, but has yet to achieve widespread usage. See Binary prefix.

1 Pronunciation
2 Common usage
3 See also
4 External links

[edit] Pronunciation

In English the initial G of giga can be pronounced with a soft G (as in gigantic) or with a hard G (as in giggle). The latter hard G pronunciation has become more common, especially when referring to computer measurements such as gigabyte and gigahertz. A prominent example of the soft G pronunciation is found in the 1985 movie Back to the Future, where gigawatts was pronounced as jigawatts.

[edit] Common usage

gigabyte — for instance, in hard disk capacity, 120 GB = 120,000,000,000 bytes; in file sizes, 1 GB = 1,073,741,824 bytes (also termed a gibibyte to reduce ambiguity)
gigahertz — clock rate of a CPU, for instance, 3 GHz = 3,000,000,000 Hz
gigabit — bandwidth of a network, for instance, 1 Gbit = 1,000,000,000 bit/s
gigayear or giga-annum — one billion (<math>10^9</math>) complete Julian rotation periods of the Earth about the Sun. (common abbr. Gyr)

SI prefixes
1000ⁿ	10ⁿ	Prefix	Symbol	Short scale	Long scale	Decimal equivalent in SI writing style
1000⁸	10²⁴	yotta	Y	Septillion	Quadrillion	1 000 000 000 000 000 000 000 000
1000⁷	10²¹	zetta	Z	Sextillion	Trilliard (thousand trillion)	1 000 000 000 000 000 000 000
1000⁶	10¹⁸	exa	E	Quintillion	Trillion	1 000 000 000 000 000 000
1000⁵	10¹⁵	peta	P	Quadrillion	Billiard (thousand billion)	1 000 000 000 000 000
1000⁴	10¹²	tera	T	Trillion	Billion	1 000 000 000 000
1000³	10⁹	giga	G	Billion	Milliard (thousand million)	1 000 000 000
1000²	10⁶	mega	M	Million		1 000 000
1000¹	10³	kilo	k	Thousand		1 000
1000^2/3	10²	hecto	h	Hundred		100
1000^1/3	10¹	deca, deka	da	Ten		10
1000⁰	10⁰	(none)	(none)	One		1
1000^−1/3	10⁻¹	deci	d	Tenth		0.1
1000^−2/3	10⁻²	centi	c	Hundredth		0.01
1000⁻¹	10⁻³	milli	m	Thousandth		0.001
1000⁻²	10⁻⁶	micro	µ (u)	Millionth		0.000 001
1000⁻³	10⁻⁹	nano	n	Billionth	Milliardth	0.000 000 001
1000⁻⁴	10⁻¹²	pico	p	Trillionth	Billionth	0.000 000 000 001
1000⁻⁵	10⁻¹⁵	femto	f	Quadrillionth	Billiardth	0.000 000 000 000 001
1000⁻⁶	10⁻¹⁸	atto	a	Quintillionth	Trillionth	0.000 000 000 000 000 001
1000⁻⁷	10⁻²¹	zepto	z	Sextillionth	Trilliardth	0.000 000 000 000 000 000 001
1000⁻⁸	10⁻²⁴	yocto	y	Septillionth	Quadrillionth	0.000 000 000 000 000 000 000 001