What is the difference between log and ln?

In math, the term log typically refers to a logarithmic function to the base of 10, while ln is the logarithmic function to the base of the constant e. Log is called a common logarithm, and ln is called a natural logarithm.

Technically, the log function can be considered to the base of any number greater than zero, although when written without additional notation, it is assumed to be to the base of 10. The constant e is known as Euler's number and is equal to approximately 2.718. A log function to the base of 2.718 would be equal to the ln.