The formal way of writing a logarithm is the following:
[tex]\log _ab[/tex]Where "a" is the base of the logarithm and "b2 is the argument.
If "a = 10", then the base is not written, like this:
[tex]\log _{10}b=\log b[/tex]In the case that the base is the constant number "e" then the logarithm is called a "natural logarithm" and it is written as follows:
[tex]\log _eb=\ln b[/tex]