sentences:  For example, in the image to the right, the neighbourhood of vertex 5 consists of vertices 1, 2 and 4 and the edge connecting vertices 1 and 2.The neighbourhood is often denoted "N""G"("v") or (when the graph is unambiguous) "N"("v").The same neighbourhood notation may also be used to refer to sets of adjacent vertices rather than the corresponding induced subgraphs.