Definition:Open Set/Complex Analysis/Definition 2

Definition

Let $S \subseteq \C$ be a subset of the set of complex numbers.

Then $S$ is an open set (of $\C$), or open (in $\C$) if and only if every point of $S$ is an interior point.

Also see

• Equivalence of Definitions of Open Set (Complex Analysis)

Sources

• 1981: Murray R. Spiegel: Theory and Problems of Complex Variables (SI ed.) ... (previous) ... (next): $1$: Complex Numbers: Point Sets: $6.$