The Real Number e

The number $e$ is an important mathematical constant, approximately equal to $2.71828$. When used as the base for a logarithm, we call the logarithm a natural logarithm and write it as $\ln x$.

The function $f(x) = e^x$ is a basic exponential function with some very interesting properties.

The natural logarithm is the logarithm to the base e, where e is an irrational and transcendental constant approximately equal to 2.718281828.