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''Giga'' ( or ) is a unit prefix in the metric system denoting a factor of a (short-form) billion (109 or ). It has the symbol G. ''Giga'' is derived from the Greek word , 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 Conference in 1947: "The following prefixes to abbreviations for the names of units should be used: G giga 109×". When referring to information units in computing, such as ''gigabyte'', ''giga'' may sometimes mean (230), although such use is inconsistent, contrary to standards and has been discouraged by the standards organizations.〔(NIST Guide for the Use of the International System of Units (Appendix D. ref 5) )〕 The inconsistency is that ''gigabit'' is never (or very rarely) used with the binary interpretation of the prefix, while ''gigabyte'' is sometimes used this way. The binary prefix ''gibi'' has been adopted for 230, while reserving ''giga'' exclusively for the metric definition. ==Pronunciation== In English, the initial ''g'' of ''giga'' can be pronounced (a hard ''g'' as in ''giggle''), or (a soft ''g'' as in ''giant'', like a ''j'' sound, which shares its Greek root).〔(A Practical Guide to the International System of Units, U.S. Metric Association, Feb 2008 )〕 This latter pronunciation was formalized within the United States in the 1960s and 1980s with the issue by the US National Bureau of Standards of pronunciation guides for the metric prefixes.〔NBS Special Publication 304 & 304A, revised August 1981, "A Brief History of Measurement Systems"〕 A prominent example is found in the pronunciation of ''gigawatts'' in the 1985 movie ''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 by the humorous poet Christian Morgenstern that appeared in the third (1908) edition of ''Galgenlieder'' (Gallows Songs). This suggests that a hard German was originally intended as the pronunciation. Self was unable to ascertain at what point the alternative pronunciation came into occasional use, but claimed that as of 1995 it had died out.〔Kevin Self, April 1995, "Technically speaking", ''Spectrum''〕 In 1998, a poll by the phonetician John C. Wells found that 84% of Britons preferred the pronunciation of ''gigabyte'' starting with (as in ''gig''), 9% with (as in ''jig''), 6% with (''guy''), and 1% with (as in ''giant'').〔Wells, J.C. (1998). ''(LPD pronunciation preference poll 1998 )''.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Giga-」の詳細全文を読む スポンサード リンク
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