A prefix appended to a unit to indicate some multiple of that unit, usually multiples of 1,000. For example:
Kilo- (K)103thousand
Mega- (M)106million
Giga- (G)109billion
Tera- (T)1012trillion
Peta- (P)1015quadrillion
Exa- (E)1018quintillion
In computing, metric prefixes are used to indicate multiple quantities of bits and bytes. For example, one kilobit is equal to approximately 1,000 bits. (Actually, since computing is based on a binary system, not a decimal one, "kilo-" is used to refer to 210, which equals 1,024, the closest number to 1,000). See Kilo-, Mega-, Giga-, Tera-, Peta-, and Exa-.