◄Summary► ◄Details► ◄Example► ◄Back► Argument number Real expression Returns <real type> Natural logarithm of number Description The Ln function returns the natural logarithm of a real number. A natural logarithm is a logarithm to the base e. The mathematical constant e is the base of the natural logarithms, and is approximately 2.71828182845905. If the argument is negative or zero, a run-time error occurs.