Giga
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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). 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×". Giga- comes from the Greek γίγας, meaning giant.