An order of magnitude.
A measure of the energy released by an earthquake (e.g. on the Richter scale).
A number, assigned to something, such that it may be compared to others numerically
The absolute or relative size, extent or importance of something.
Of a vector, the norm, most commonly, the two-norm.
The apparent brightness of a star, with lower magnitudes being brighter; apparent magnitude
A ratio of intensity expressed as a logarithm.
The 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 10² = 100, 10³ = 1000, and 10⁶ = a million.