# Definition:Incident (Graph Theory)/Undirected Graph

## Definition

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

Let $u, v \in V$ be vertices of $G$.

Let $e = \set {u, v} \in E$ be an edge of $G$:

Then:

$u$ and $v$ are each incident with $e$
$e$ is incident with $u$ and incident with $v$.

## Also known as

It is common to see incident to being used for incident with. For undirected graphs this is appropriate; for directed graphs the situation is more complicated.

Some sources use incident on.