Definition

Directed Acyclic Graph, DAG is a finite directed graph with no directed cycles, it has a finite number of vertices (nodes) and edges (paths), whereby every edge directs from one vertiex to the other, follows a consistently-directed sequence of edges that does not loop back to the start node

Graphs are ubiquitous, they can be used to model directed or undirected connectivities in the real world.

A set of vertices {v₁, v₂, ..v_n}
and a set of edges {e₁, e₂, ..e_m}

An edge is defined as a pair of connected vertices
{v_i, v_j}, where i,j ∈ {1,...n}