directed graph
noun
°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.
"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."
synonyms: digraph