\begin{definition}[Definition:Adjacent (Graph Theory)/Faces]
Let $G = \left({V, E}\right)$ be a planar graph.
Two faces of $G$ are '''adjacent''' {{iff}} they are both incident to the same edge (or edges).
Note that faces which are both incident to the same vertex are ''not'' considered adjacent unless they are also both incident to the same edge.
Category:Definitions/Graph Theory
\end{definition}