As a mathematical constant, e is the base of natural logarithmic function. It is sometimes called Euler number, named after the Swiss mathematician Euler. There is also a relatively rare name, Napier constant, to commemorate the Scottish mathematician John? Napier introduced logarithm. It is one of the most important constants in mathematics, just like pi and imaginary units I and E.

In mathematics, e means defining the function f (x) = (1+1/x) x. When x approaches infinity, this function has a limit, which is an irrational number.