What is the notation for a logarithm with base 10?

The logarithm of a number with base=B is written as [ logB(N) ].

If the base is 10, it's called the "common logarithm" of N and the base isn't written. [ log(N) ].

If the base is 'e', it's called the "natural logarithm" of N, and written [ ln(N) ].