Definition:Adjacent (Graph Theory)/Vertices/Undirected Graph

Definition
Let $G = \left({V, E}\right)$ be an undirected graph.

Two vertices $u, v \in V$ of $G$ are adjacent if there exists an edge $e = \left\{{u, v}\right\} \in E$ of $G$ to which they are both incident.

Otherwise they are non-adjacent.

Also known as
Adjacent vertices can also be described as neighboring (British English spelling: neighbouring).