Refer to the glossary of graph theory for basic definitions in graph theory.
Definitions in graph theory vary. The following are some of the more basic ways of defining graphs and related mathematical structures.
A graph with three vertices and three edges.
In one restricted but very common sense of the term, a graph is an ordered pair comprising:
- , a set of vertices (also called nodes or points);
- , a set of edges (also called links or lines), which are unordered pairs of vertices (that is, an edge is associated with two distinct vertices).
To avoid ambiguity, this type of object may be called precisely an undirected simple graph.
In the edge , the vertices