Mathematical logarithm represents logarithm. In general, the function y = logax(a >；; 0, and a≠ 1) is called logarithmic function, that is, a function with power (real number) as independent variable, exponent as dependent variable and base constant as constant is called logarithmic function.

Usually, we call the logarithm with 10 as the common logarithm, and record log 10N as lgN. In addition, the logarithm based on irrational number e=2.7 1828 is often used in scientific counting. The logarithm based on E is called natural logarithm, and logeN is recorded as InN.