Giga-

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 unit prefix in the metric system denoting a factor of a short-scale billion or long-scale milliard (109 or 1,000,000,000). It has the symbol '''G'''.

''Giga-'' is derived from the Greek word {{lang|grc|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×."<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}} (230); this causes ambiguity. Standards organizations discourage this and use giga- to refer to 109 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 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. }}</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 230, while reserving ''giga'' exclusively for the metric definition.

==Pronunciation== In 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 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 {{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= |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. 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 CPU, for instance, 3 GHz = {{gaps|3|000|000|000|Hz}} * gigabit—bandwidth of a 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 (109) 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 (230) bytes. Per IEC 60027-2 A.2 and ISO/IEC 80000 standards, the correct notation of 230 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 approximately {{val|1.074|u=GB}}. Despite international standards, the use of {{val|1|u=GB}} = 230 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>

==References== {{reflist}}

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

Category:SI prefixes

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