noun
(physics and astrophysics)
An order or factor of ten. Used both to refer to the function \mathrm{dex}(x) = 10^x and the number of (possibly fractional) orders of magnitude separating two numbers. When dealing with log to the base 10 transform of a number set the transform of 10, 100, and 1 000 000 is \log_{10}(10) = 1, \log_{10}(100) = 2, and \log_{10}(1 000 000) = 6, so the difference between 10 and 100 in base 10 is 1 dex and the difference between 1 and 1 000 000 is 6 dex.