lecture- graphs terminology graph consists ofa setvof vertices (nodesa collectioneof pairs of vertices from called edges (arcsedgesalso called arcsare represented by (uvand are eitherdirected if the pairs are ordered (uvu the origin the destination undirected if the pairs are unordered graph is pictorial representation of set of objects where some pairs of objects are connected by links the interconnected objects are represented by points termed as verticesand the links that connect the vertices are called edges formallya graph is pair of sets (ve)where is the set of vertices and eis the set of edgesconnecting the pairs of vertices take look at the following graph in the above graphv {abcdee {abacbdcddethen graph can bedirected graph (di-graphif all the edges are directed undirected graph (graphif all the edges are undirected mixed graph if edges are both directed or undirected illustrate terms on graphs end-vertices of an edge are the endpoints of the edge two vertices are adjacent if they are endpoints of the same edge an edge is incident on vertex if the vertex is an endpoint of the edge outgoing edges of vertex are directed edges that the vertex is the origin incoming edges of vertex are directed edges that the vertex is the destination degree of vertexvdenoted deg(vis the number of incident edges out-degreeoutdeg( )is the number of outgoing edges in-degreeindeg( )is the number of incoming edges parallel edges or multiple edges are edges of the same type and end-vertices self-loop is an edge with the end vertices the same vertex