In mathematics, a logarithm (to base b) of a number x is written logb(x) and equals the exponent y that satisfies x = by.
The base b must be neither 0 nor 1 (nor a root of 1 in the case of the extension to complex numbers, the complex logarithm), and is typically 10, e, or 2. When x and b are further restricted to positive real numbers, the logarithm is a unique real number.