\begin{definition}[Definition:Incident (Graph Theory)/Planar Graph]
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Let $G = \left({V, E}\right)$ be a planar graph:
Then a face of $G$ is '''incident to''' an edge $e$ of $G$ if $e$ is one of those which surrounds the face.
Similarly, a face of $G$ is '''incident to''' a vertex $v$ of $G$ if $v$ is at the end of one of those incident edges.
In the above graph, for example, the face $ABHC$ is incident to:
: the edges $AB, BH, HC, CA$
: the vertices $A, B, H, C$.
Category:Definitions/Graph Theory
\end{definition}