Definition:Bounded Mapping/Complex-Valued

Definition
Let $f: S \to \C$ be a complex-valued function.

Then $f$ is bounded the real-valued function $\cmod f: S \to \R$ is bounded, where $\cmod f$ is the modulus of $f$.

That is, $f$ is bounded if there is a constant $K \ge 0$ such that $\cmod {\map f z} \le K$ for all $z \in S$.

Also see

 * Complex Plane is Metric Space: this definition coincides with the definition of a bounded mapping to a metric space, using the standard metric on $\C$.