A unit of frequency equal to 109 per second, or 1 per nanosecond. Cellular phones and microwave ovens operate with radio waves having frequencies in the gigahertz range
Russ Rowlett (Director), How Many? A Dictionary of Units of Measurement, Center for Mathematics and Science Education University of North Carolina, USA 2005. http://www.unc.edu/~rowlett/units/dictA.html, (Unit of Meas and Covr Factors - Amer) {608}