Graph loop

A loop is where a vertex on a graph has an edge that connects back to itself. In other words, the edge starts and ends at the same vertex.

A loop is an edge that connects a vertex to itself.

Loops and vertex degrees

• If a vertex has a loop, its degree increases by 2, since the loop technically attaches to the vertex twice (once at each end).
• This only applies if the graph is not directed.

Simple graphs

• A simple graph is a graph that does not allow loops or multiple edges between the same pair of vertices.
• This means that loops can’t exist in simple graphs.