Topics: Graph Theory
The set of edges in a given graph can be empty. An edge that joins the same vertex is called a loop.
Adjacency and Incidency
When two edges share a vertex, we say that they are adjacent.
When a vertex is a final node of an edge , we say that incides on .
Edges can be of two types: undirected or directed (also known as arcs). Directed edges have a direction, while undirected edges do not.
An example of an undirected edge is:
An example of a directed edge is: