The natural logarithm, written mathematically as , is a specific case of the more familiar logarithms, denoted mathematically as . All logarithms must have a base value. If the base is not specified, as in the case of , the base can be assumed to be ten (the common logarithm). The same holds true of the natural logarithm, which has an inherently defined base of value (Euler's number), which recognized by the form the function takes: . * Common Logarithm: * Arbitrary Base Logarithm: * Natural Logarithm: