View source for Giga-

{{Short description|Metric prefix}}
{{Other uses|Giga (disambiguation)}}

[[File:Laptop-hard-drive-exposed.jpg|thumb|alt=Laptop-hard-drive-exposed|Laptop hard drive, with its platter exposed.]]
'''Giga-''' ({{IPAc-en|ˈ|g|ɪ|g|ə}} or {{IPAc-en|ˈ|dʒ|ɪ|g|ə}}) is a [[metric prefix|unit prefix]] in the [[metric system]] denoting a factor of a [[Long and short scales|short-scale]] billion or long-scale [[milliard]] (10<sup>9</sup> or [[1,000,000,000]]). It has the symbol '''G'''.

''Giga-'' is derived from the [[Ancient Greek|Greek]] word {{lang|grc|γίγας}} (''gígas''), meaning "[[wikt:giant|giant]]". The ''[[Oxford English Dictionary]]'' reports the earliest written use of ''giga'' in this sense to be in the Reports of the [[International Union of Pure and Applied Chemistry|IUPAC]] 14th Conférence Internationale de Chimie in 1947: "The following prefixes to abbreviations for the names of units should be used: G giga 10<sup>9</sup>×."<ref>{{Cite web|url=http://www.oed.com/view/Entry/78201|title=giga-, comb. form|date=October 2011|website=Oxford English Dictionary}}</ref> However, it was already used in 1932 by the German organization ''Verband deutscher Elektrotechniker''.<ref>{{Cite web |url=https://worldradiohistory.com/UK/Experimental-Wireless/30s/Wireless-Engineer-1932-05-S-OCR.pdf |title=Wireless Engineer, 1932, issue 05, p. 252. |access-date=2022-03-28 |archive-date=2022-03-28 |archive-url=https://web.archive.org/web/20220328040119/https://worldradiohistory.com/UK/Experimental-Wireless/30s/Wireless-Engineer-1932-05-S-OCR.pdf |url-status=live }}</ref>

When referring to information units in [[computing]], such as [[gigabyte]], giga may sometimes mean {{gaps|1|073|741|824}} (2<sup>30</sup>); this causes ambiguity. [[Standards organization]]s discourage this and use giga- to refer to 10<sup>9</sup> in this context too.<ref name="BIPM">{{cite book
|title=The International System of Units (SI)
|url=http://www1.bipm.org/utils/common/pdf/si_brochure_8.pdf |archive-url=https://web.archive.org/web/20060813144253/http://www.bipm.org/utils/common/pdf/si_brochure_8.pdf |archive-date=2006-08-13 |url-status=live
|access-date=2007-02-25
|edition=8th
|year=2006
|publisher=STEDI Media
|location=Paris
|language=fr, en
|isbn=92-822-2213-6
|pages=127
|chapter=§3.1 SI prefixes
|quote=[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 2<sup>10</sup>, 2<sup>20</sup>, 2<sup>30</sup>, 2<sup>40</sup>, 2<sup>50</sup>, and 2<sup>60</sup> are, respectively: kibi, Ki; mebi, Mi; gibi, Gi; tebi, Ti; pebi, Pi; and exbi, Ei. Thus, for example, one kibibyte would be written: 1&nbsp;KiB = 2<sup>10</sup> 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.
}}</ref><ref name="NIST">[http://physics.nist.gov/cuu/pdf/sp811.pdf NIST Guide for the Use of the International System of Units (Appendix D. ref 5)]</ref>{{primary source inline|date=October 2020}} ''Gigabit'' is only rarely used with the binary interpretation of the prefix. The [[binary prefix]] gibi has been adopted for 2<sup>30</sup>, while reserving ''giga'' exclusively for the metric definition.

==Pronunciation==
In [[English language|English]], the prefix ''giga'' can be pronounced {{IPAc-en|ˈ|ɡ|ɪ|ɡ|ə}} (a hard ''g'' as in ''giggle''), or {{IPAc-en|ˈ|dʒ|ɪ|g|ə}} (a soft ''g'' as in ''gigantic'', which shares ''giga''{{'s}} Ancient Greek root).<ref>{{cite web |title=SI prefixes and their etymologies |url=https://usma.org/si-prefixes-and-their-etymologies |website=US Metric Association |access-date=27 November 2019}}</ref> 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 10<sup>9</sup> 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 {{lang|de|Galgenlieder}} (Gallows Songs).<ref>{{cite book |author-last=Morgenstern |author-first=Christian |author-link=Christian Morgenstern |others=Illustrated by [[Karl Walser]] |title={{lang|de|Galgenlieder nebst dem 'Gingganz'}} |date=1917 |publisher=Bruno Cassirer |via=[[Project Gutenberg]] |location=Berlin, Germany |page=52 |edition=22 |language=de |quote=''[First four lines:]'' {{lang|de|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!|italic=unset}}}} [These lines are the only appearance of ''gig'' in the book. {{lang|de|Gigant}} is German for "giant"; cf. "gigantic".]</ref><ref>{{cite book |author-last=Morgenstern |author-first=Christian |author-link=Christian Morgenstern |title=Gallows Songs: Christian Morgenstern's "Galgenlieder", Bilingual Edition: A Selection |date=1963 |translator-last=Knight |translator-first=Max |translator-link=Max Knight |publisher=University of California Press |isbn=9780520008847 |pages=24–25 |url=https://books.google.com/books?id=bPLXx5DYnT8C&pg=PA24 |access-date=20 February 2016 |quote=''[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.)}}</ref> This suggests that a hard German {{IPA|[ɡ]}} was originally intended as the pronunciation. Self was unable to ascertain when the {{IPA|/dʒ/}} (soft ''g'') pronunciation came into occasional use, but claimed that as of 1995 it had returned to {{IPA|/ɡ/}} (hard ''g'').<ref>{{cite journal |author-last=Self |author-first=Kevin |title=Technically speaking |journal=Spectrum |page=18 |publisher=[[IEEE]] |date=October 1994}}</ref><ref>{{cite journal |author-last=Self |author-first=Kevin |title=Technically speaking |journal=Spectrum |page=16 |publisher=[[IEEE]] |date=April 1995}}</ref>

In 1998, a poll by the phonetician [[John C. Wells]] found that 84% of Britons preferred the pronunciation of ''gigabyte'' starting with {{IPA|/ɡɪ/}} (as in ''gig''), 9% with {{IPA|/dʒɪ/}} (as in ''jig''), 6% with {{IPA|/ɡaɪ/}} (''guy''), and 1% with {{IPA|/dʒaɪ/}} (as in ''giant'').<ref>Wells, J.&nbsp;C. (1998). ''[http://www.phon.ucl.ac.uk/home/wells/poll98.htm LPD pronunciation preference poll 1998]''.</ref>

==Common usage==
* [[gigahertz]]—[[clock rate]] of a [[Central processing unit|CPU]], for instance, 3&nbsp;GHz = {{gaps|3|000|000|000|[[Hertz|Hz]]}}
* [[gigabit]]—[[Bandwidth (computing)|bandwidth]] of a [[computer network|network]] link, for instance, 1 Gbit/s = {{gaps|1|000|000|000|[[bit]]/s}}.
* [[gigabyte]]—for instance, for [[hard disk]] capacity, 120 GB = {{gaps|120|000|000|000|bytes}};
* [[gigayear]] or [[gigaannum]]—one billion (10<sup>9</sup>) years, sometimes abbreviated Gyr, but the preferred usage is Ga or, for ''years ago'', GA.<ref>{{Cite journal |last=Wilcock |first=Bruce |date=July 1967 |title=Megayear and Gigayear |url=https://www.nature.com/articles/215102b0 |journal=Nature |language=en |volume=215 |issue=5096 |pages=102–102 |doi=10.1038/215102b0 |issn=1476-4687}}</ref>

==Binary prefix==
The notation {{val|1|u=GB}} represents 1,000,000,000 bytes or, in deprecated usage, 1,073,741,824 (2<sup>30</sup>) bytes. Per IEC 60027-2 A.2 and ISO/IEC 80000 standards, the correct notation of 2<sup>30</sup> is ''[[gibi]]'' (symbol Gi).<ref>{{Cite web |title=Definitions of the SI units: The binary prefixes |url=https://physics.nist.gov/cuu/Units/binary.html |access-date=2023-04-05 |website=physics.nist.gov}}</ref> One [[gibibyte]] ({{val|1|u=GiB}}) is 1,073,741,824 bytes or {{val|1.074|u=GB}}. Despite international standards, the use of {{val|1|u=GB}} = 2<sup>30</sup>&nbsp;B is widespread. A laptop advertised as having {{val|8|u=GB}} has 8,589,934,592 bytes of memory: {{val|8.59|e=9|u=B}}, or {{val|8|u=GiB}}. <ref>{{Cite web |title=GB Vs GiB: What’s The Difference? - MASV |url=https://massive.io/file-transfer/gb-vs-gib-whats-the-difference/ |access-date=2024-08-08 |website=massive.io |language=en}}</ref>

==See also==
* [[Binary prefix]]
* [[Gigabit Ethernet]]
* [[SI prefix]]
* [[List of commonly used taxonomic affixes]]
* [[RKM code]]

==References==
{{reflist}}

==External links==
{{wiktionary|giga-}}
* [http://www.bipm.org BIPM website]

{{SI prefixes (infobox)}}

[[Category:SI prefixes]]

[[he:תחיליות במערכת היחידות הבינלאומית#גיגה]]