Editing Loop (graph theory) (section)

==Degree==
For an [[undirected graph]], the [[degree (graph theory)|degree]] of a vertex is equal to the number of [[adjacent vertex|adjacent vertices]].

A special case is a loop, which adds two to the degree. This can be understood by letting each connection of the loop edge count as its own adjacent vertex. In other words, a vertex with a loop "sees" itself as an adjacent vertex from ''both'' ends of the edge thus adding two, not one, to the degree.

For a [[directed graph]], a loop adds one to the [[in degree (graph theory)|in degree]] and one to the [[out degree (graph theory)|out degree]].