Giga-
Giga- is a unit prefix in the metric system denoting a factor of a short-scale billion or long-scale milliard. It has the symbol G.
Giga- is derived from the Greek word γίγας, 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×." However, it was already used in 1932 by the German organization Verband deutscher Elektrotechniker.
When referring to information units in computing, such as gigabyte, giga may sometimes mean ; this causes ambiguity. Standards organizations discourage this and use giga- to refer to 109 in this context too. 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 , or . 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 by the German humorous poet Christian Morgenstern that appeared in the third edition of his Galgenlieder. This suggests that a hard German was originally intended as the pronunciation. Self was unable to ascertain when the pronunciation came into occasional use, but claimed that as of 1995 it had returned to .
In 1998, a poll by the phonetician John C. Wells found that 84% of Britons preferred the pronunciation of gigabyte starting with , 9% with , 6% with , and 1% with .
Common usage
- gigahertz—clock rate of a CPU, for instance, 3 GHz =
- gigabit—bandwidth of a network link, for instance, 1 Gbit/s =.
- gigabyte—for instance, for hard disk capacity, 120 GB = ;
- gigayear or gigaannum—one billion years, sometimes abbreviated Gyr, but the preferred usage is Ga or, for years ago, GA.
Binary prefix