applications of graph , edges , linear graph , selfloop , simple graph , vertices , what is a graph Edit
Definition also permits an edge to be associated with a vertex pair (vi,vi) such an edge having the same vertex as both its end vertices is called self loop. V2 is having self loop.
The definition also permits more than one edge associated with a given pair of vertices, such edges are called parallel edges. Such as e4 and e5 of the following graph.