# The Natural Log

Another special type of logarithm you'll see from time to time is the **natural logarithm**, usually written as ln(*x*) instead of log(*x*). We like to think the "n" comes after the "l" because it stands for log au naturel.

A natural log is the same as a regular log, except it has a base of *e *instead of 10. If you haven't met him before, *e* is an irrational number that represents the sum of and so on.

Weird, right? But it's really useful! You'll see the natural log all the time in higher-level math, but we'll show you a common use in a later chapter. For now, just remember this:

ln *x* = log_{e}*x*

To confuse things, some people write ln *x* as log* _{e} x *or even log

*x*. We wouldn't do that; keep an eye out, though!