A logarithm is a number that indicates an exponent used to raise a logarithm's base in order to get back an indicated number. The logarithm of a positive number can be written where indicates which base has been used. The expression is read as "log, base-, of " or "base- log ".
For example, since is the exponent used to raise the base to get the number Logarithms are undefined for negative values of
The result of a logarithm depends on the base of the logarithm. Log base 4 indicates that the base is while log base 9 has the base If the base of the logarithm is changed the result of the logarithm becomes something else entirely.