Giga-

Giga (/ˈɡɪɡə/ or /ˈdʒɪɡə/) is a unit prefix in the metric system denoting a factor of a short-scale billion or long-scale milliard (10⁹ or 1000000000). It has the symbol G.

Giga is derived from the Greek word γίγας (gígas), meaning "giant". The Oxford English Dictionary reports the earliest written use of giga in this sense to be in the Reports of the IUPAC 14th Conférence Internationale de Chimie in 1947: "The following prefixes to abbreviations for the names of units should be used: G giga 10⁹×."[1]

When referring to information units in computing, such as gigabyte, giga may sometimes mean 1073741824 (2³⁰); this causes ambiguity. Standards organizations discourage this and use giga- to refer to 10⁹ in this context too.[2][3] Gigabit is only rarely used with the binary interpretation of the prefix. The binary prefix gibi has been adopted for 2³⁰, while reserving giga exclusively for the metric definition.

Pronunciation

In English, the prefix giga can be pronounced /ˈɡɪɡə/ (a hard g as in giggle), or /ˈdʒɪɡə/ (a soft g as in gigantic, which shares giga's Ancient Greek root).[4]

A prominent example of this latter pronunciation is found in the pronunciation of gigawatts in the 1985 film Back to the Future.

According to the American writer Kevin Self, a German committee member of the International Electrotechnical Commission proposed giga as a prefix for 10⁹ in the 1920s, drawing on a verse (evidently "Anto-logie") by the German humorous poet Christian Morgenstern that appeared in the third (1908) edition of his Galgenlieder (Gallows Songs).[5][6] This suggests that a hard German [ɡ] was originally intended as the pronunciation. Self was unable to ascertain when the /dʒ/ (soft g) pronunciation came into occasional use, but claimed that as of 1995 it had returned to /ɡ/ (hard g).[7][8]

In 1998, a poll by the phonetician John C. Wells found that 84% of Britons preferred the pronunciation of gigabyte starting with /ɡɪ/ (as in gig), 9% with /dʒɪ/ (as in jig), 6% with /ɡaɪ/ (guy), and 1% with /dʒaɪ/ (as in giant).[9]

Common usage

gigahertz—clock rate of a CPU, for instance, 3 GHz = 3000000000Hz
gigabit—bandwidth of a network link, for instance, 1 Gbit/s = 1000000000bit/s.
gigabyte—for instance, for hard disk capacity, 120 GB = 120000000000bytes;
gigayear or gigaannum—one billion (10⁹) years, sometimes abbreviated Gyr, but the preferred usage is Ga.

SI prefixes
Prefix		Base 10	Decimal	Adoption [nb 1]
Name	Symbol	Base 10	Decimal	Adoption [nb 1]
quetta	Q	10³⁰	1000000000000000000000000000000	2022[10]
ronna	R	10²⁷	1000000000000000000000000000	2022[10]
yotta	Y	10²⁴	1000000000000000000000000	1991
zetta	Z	10²¹	1000000000000000000000	1991
exa	E	10¹⁸	1000000000000000000	1975[11]
peta	P	10¹⁵	1000000000000000	1975[11]
tera	T	10¹²	1000000000000	1960
giga	G	10⁹	1000000000	1960
mega	M	10⁶	1000000	1873
kilo	k	10³	1000	1795
hecto	h	10²	100
deca	da	10¹	10
—	—	10⁰	1	—
deci	d	10⁻¹	0.1	1795
centi	c	10⁻²	0.01
milli	m	10⁻³	0.001
micro	μ	10⁻⁶	0.000001	1873
nano	n	10⁻⁹	0.000000001	1960
pico	p	10⁻¹²	0.000000000001	1960
femto	f	10⁻¹⁵	0.000000000000001	1964
atto	a	10⁻¹⁸	0.000000000000000001	1964
zepto	z	10⁻²¹	0.000000000000000000001	1991
yocto	y	10⁻²⁴	0.000000000000000000000001	1991
ronto	r	10⁻²⁷	0.000000000000000000000000001	2022[10]
quecto	q	10⁻³⁰	0.000000000000000000000000000001	2022[10]
Notes Prefixes adopted before 1960 already existed before SI. The introduction of the CGS system was in 1873.

Binary prefix

The notation 1 GB represents 1,000,000,000 bytes or, in deprecated usage, 1,073,741,824 (2³⁰) bytes. Per IEC 60027-2 A.2 and ISO/IEC 80000 standards, the correct notation of 2³⁰ is gibi (symbol Gi).[12] One gibibyte (1 GiB) is 1,073,741,824 bytes or 1.074 GB. Despite international standards, the use of 1 GB = 2³⁰ B is widespread. A laptop advertised as having 8 GB has 8,589,934,592 bytes of memory: 8.59×10⁹ B, or 8 GiB.

References

"giga-, comb. form". Oxford English Dictionary. October 2011.
"§3.1 SI prefixes". The International System of Units (SI) (PDF) (in French and English) (8th ed.). Paris: STEDI Media. 2006. p. 127. ISBN 92-822-2213-6. Archived (PDF) from the original on 2006-08-13. Retrieved 2007-02-25. [Side note:] These SI prefixes refer strictly to powers of 10. They should not be used to indicate powers of 2 (for example, one kilobit represents 1000 bits and not 1024 bits). The IEC has adopted prefixes for binary powers in the international standard IEC 60027-2: 2005, third edition, Letter symbols to be used in electrical technology — Part 2: Telecommunications and electronics. The names and symbols for the prefixes corresponding to 2¹⁰, 2²⁰, 2³⁰, 2⁴⁰, 2⁵⁰, and 2⁶⁰ are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1 KiB = 2¹⁰ B = 1024 B, where B denotes a byte. Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes.
NIST Guide for the Use of the International System of Units (Appendix D. ref 5)
"SI prefixes and their etymologies". US Metric Association. Retrieved 27 November 2019.
Morgenstern, Christian (1917). Galgenlieder nebst dem 'Gingganz' (in German). Illustrated by Karl Walser (22 ed.). Berlin, Germany: Bruno Cassirer. p. 52 – via Project Gutenberg. [First four lines:] Im Anfang lebte, wie bekannt, / als größter Säuger der Gig-ant. / Wobei gig eine Zahl ist, die / es nicht mehr gibt, - so groß war sie! [These lines are the only appearance of gig in the book. Gigant is German for "giant"; cf. "gigantic".]
Morgenstern, Christian (1963). Gallows Songs: Christian Morgenstern's "Galgenlieder", Bilingual Edition: A Selection. Translated by Knight, Max. University of California Press. pp. 24–25. ISBN 9780520008847. Retrieved 20 February 2016. [Translation:] Of yore, on earth was dominant / the biggest mammal: the Gig-ant. / ("Gig" is a numeral so vast, / it's been extinct for ages past.)
Self, Kevin (October 1994). "Technically speaking". Spectrum. IEEE: 18.
Self, Kevin (April 1995). "Technically speaking". Spectrum. IEEE: 16.
Wells, J. C. (1998). LPD pronunciation preference poll 1998.
"On the extension of the range of SI prefixes". 18 November 2022. Retrieved 5 February 2023.
"Metric (SI) Prefixes". NIST.
"Definitions of the SI units: The binary prefixes". physics.nist.gov. Retrieved 2023-04-05.

External links

BIPM website

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[10] Prefixes adopted before 1960 already existed before SI. The introduction of the CGS system was in 1873.

[1] "giga-, comb. form". Oxford English Dictionary. October 2011.

[BIPM-2] "§3.1 SI prefixes". The International System of Units (SI) (PDF) (in French and English) (8th ed.). Paris: STEDI Media. 2006. p. 127. ISBN 92-822-2213-6. Archived (PDF) from the original on 2006-08-13. Retrieved 2007-02-25. [Side note:] These SI prefixes refer strictly to powers of 10. They should not be used to indicate powers of 2 (for example, one kilobit represents 1000 bits and not 1024 bits). The IEC has adopted prefixes for binary powers in the international standard IEC 60027-2: 2005, third edition, Letter symbols to be used in electrical technology — Part 2: Telecommunications and electronics. The names and symbols for the prefixes corresponding to 2¹⁰, 2²⁰, 2³⁰, 2⁴⁰, 2⁵⁰, and 2⁶⁰ are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1 KiB = 2¹⁰ B = 1024 B, where B denotes a byte. Although these prefixes are not part of the SI, they should be used in the field of information technology to avoid the incorrect usage of the SI prefixes.

[NIST-3] NIST Guide for the Use of the International System of Units (Appendix D. ref 5)

[4] "SI prefixes and their etymologies". US Metric Association. Retrieved 27 November 2019.

[5] Morgenstern, Christian (1917). Galgenlieder nebst dem 'Gingganz' (in German). Illustrated by Karl Walser (22 ed.). Berlin, Germany: Bruno Cassirer. p. 52 – via Project Gutenberg. [First four lines:] Im Anfang lebte, wie bekannt, / als größter Säuger der Gig-ant. / Wobei gig eine Zahl ist, die / es nicht mehr gibt, - so groß war sie! [These lines are the only appearance of gig in the book. Gigant is German for "giant"; cf. "gigantic".]

[6] Morgenstern, Christian (1963). Gallows Songs: Christian Morgenstern's "Galgenlieder", Bilingual Edition: A Selection. Translated by Knight, Max. University of California Press. pp. 24–25. ISBN 9780520008847. Retrieved 20 February 2016. [Translation:] Of yore, on earth was dominant / the biggest mammal: the Gig-ant. / ("Gig" is a numeral so vast, / it's been extinct for ages past.)

[7] Self, Kevin (October 1994). "Technically speaking". Spectrum. IEEE: 18.

[8] Self, Kevin (April 1995). "Technically speaking". Spectrum. IEEE: 16.

[9] Wells, J. C. (1998). LPD pronunciation preference poll 1998.

[newUnitAdoption-11] "On the extension of the range of SI prefixes". 18 November 2022. Retrieved 5 February 2023.

[12] "Metric (SI) Prefixes". NIST.

[13] "Definitions of the SI units: The binary prefixes". physics.nist.gov. Retrieved 2023-04-05.