Definition of "logarithm"

(mathematics) For a number x , the power to which a given base number must be raised in order to obtain x . Written log b ⁡ x . For example, log 10 ⁡ 1000 = 3 because 10 3 = 1000 and log 2 ⁡ 16 = 4 because 2 4 = 16 .  examples