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

## Definition

Let $G = \struct {V, E}$ be an undirected graph.

Two vertices $u, v \in V$ of $G$ are adjacent if there exists an edge $e = \set {u, v} \in E$ 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).