An incidence list contains a list for the edges incident to a vertex for each vertex in the graph. Thus, the incidence list contains a row for each vertex. For each edge that is stored in the incidence list, there needs to be extra information stored about what the endpoint of that edge is. For example, there could be three vertexes A, B , and C with edges A1 ( that starts at A and ends at B ) and A2 ( that starts at A and ends at C ). The incidence list contains edges A1 and A2 for vertex A and nothing for B and C. The edge A1 would need to store both A1 and B and A2 would need to store both A2 and C.