E is a real number. She is a special real number, which we call transcendental number. It is said that it was first introduced from calculating the limit when (1+ 1/x) x tends to infinity.

Of course, there are many other methods to calculate e, such as e =1+11! + 1/2! + 1/3! +? .

As a mathematical constant, e is the basis of natural logarithmic function. Sometimes called Euler number, named after the Swiss mathematician Euler; There is also a relatively rare name Napier constant to commemorate the introduction of logarithm by Scottish mathematician John Napier.

It is one of the most important constants in mathematics, just like pi and imaginary units I and E.