The natural logarithm of a number is its logarithm to the base of the mathematical constant e, which is an irrational and transcendental number approximately equal to 2.718281828459. The natural logarithm of x is generally written as ln x, loge x, or sometimes, if the base e is implicit, simply log x. The natural logarithm is the inverse of e^x, which is a scaling factor that shows how much growth we would get after x units of time. The natural logarithm is used to calculate the amount of time it would take to achieve a certain level of growth. For example, ln(1) is zero because it doesnt take any time to grow from 1 to 1, while ln(2) is the amount of time it would take to double. Natural logarithms only have base e, which is approximately equal to 2.718.