Graph (Discrete Mathematics)

In discrete mathematics, particularly graph theory, a graph is a structure consisting of a set of objects, called vertices, in which some pairs are related by connections called edges; a graph is typically depicted as dots or circles for vertices joined by lines or curves for edges. Edges may be directed or undirected: an edge between two people who shook hands is undirected, since the relation is necessarily mutual, while an edge from a person who owes another money is directed, since owing is not necessarily reciprocated. The word graph was first used in this mathematical sense by J. J. Sylvester in 1878, drawing a direct relation between mathematics and chemical structure.