1.nounThe class of scale or magnitude of any amount, where each class contains values of a fixed ratio (most often 10) to the class preceding it. For example, something that is 2 orders of magnitude larger is 100 times larger, something that is 3 orders of magnitude larger is 1000 times larger, and something that is 6 orders of magnitude larger is a million times larger, because 10^2 = 100, 10^3 = 1000, and 10^6 = a million.