\begin{definition}[Definition:Ordinary Mean Value]
Let $f: \N \to \C$ be an arithmetic function.
The '''(ordinary) mean value''' of $f$ is the limit:
:$\map M f = \ds \lim_{x \mathop \to \infty} \frac 1 x \sum_{n \mathop \le x} \map f n$
if it exists.
\end{definition}