<b>Directed acyclic graph</b>
In mathematics, particularly graph theory, and computer science, a directed acyclic graph (DAG  (listen)), is a finite directed graph with no directed cycles. That is, it consists of finitely many vertices and edges (also called arcs), with each edge directed from one vertex to another, such that there is no way to start at any vertex v and follow a consistently-directed sequence of edges that eventually loops back to v again. Equivalently, a DAG is a directed graph that has a topological ordering, a sequence of the vertices such that every edge is directed from earlier to later in the sequence.
DAGs can model many different kinds of information.