The natural log is the logarithm to the base of the number e and is the inverse function of an exponential function. Natural logarithm is particular case of logarithms and is typically used in solving time, growth/decay problems.
The number 'e' is an irrational constant approximately equal to 2.718281828459. The natural logarithm of x is generally written as ln(x) or logex.
The natural logarithm of x is the power to which e would have to be raised to equal x. For example, ln(10) is 2.30258509..., because e2.30258509... = 10