Definition:Incident (Planar Graph)

Definition

Let $G = \left({V, E}\right)$ be a planar graph:

Then a face of $G$ is incident to an edge if the edge is one of those which surrounds the face.

Similarly, a face of $G$ is incident to a vertex if the vertex 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 $A, B, H, C$.