Noun
directed graph (plural directed graphs)
(graph theory) A graph in which the edges are ordered pairs, so that, if the edge (a, b) is in the graph, the edge (b, a) need not be in the graph and is distinct from (a, b) if it is.
Synonym: digraph
Antonym: undirected graph
A directed graph (A, R) is a set of vertices A together with an incidence relation R: if aRb then there is an edge going from A to B.