Definition:Exterior Point (Complex Analysis)/Definition 1

Definition
Let $S \subseteq \C$ be a subset of the complex plane.

Let $z_0 \in \C$.

$z_0$ is an exterior point of $S$ iff $z_0$ has an $\epsilon$-neighborhood which is disjoint from $S$.

Also see

 * Equivalence of Definitions of Exterior Point (Complex Analysis)