giga-

In units of measurement, a factor of one thousand million or 10⁹. In computing, often a factor of 2³⁰ (1,073,741,824).

Greek gigas, giant.

This is one of the standard SI (Système International) decimal prefixes (see the entry Number words), which appears in such compounds as gigahertz and gigawatt. Computer science has borrowed the unit—as it has with others—to refer to powers of 2 rather than 10, so that a gigabyte, for example, is usually taken to be 2³⁰ bytes. This is true also of other computer terms such as gigabit or gigaflops (strictly 2³⁰ floating-point operations per second).