logarithm

A function expressing any number by the exponent of a chosen base. E.g., with 512=2**9, the dual logarithm (to the base 2) of 512, written log_2 512 equals 9. Logarithms are used in the quantitative definition of information and are fundamental to the algebraic properties which information theory codifies. Its base of 2 assures the interpretation of that at function in terms of the number of binary decisionS (see bits). Decimal logarithms have a base of 10 and natural logarithms a base of 2.71828. (Krippendorff)