Another name for the bel or the order of magnitude: a logarithmic unit used to compare the sizes of quantities. Two quantities differ by one decade if one is 10 times the other, by two decades if one is 10·10 = 100 times the other, and so on
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}