1. NG(v)
2. G[X,Y]
3. length of a path or circle
4. k-path or k-circle
5. construction of graph
   1. vertices
      1. neighbours
         1. adjacent
   2. edges
      1. ends
      2. parallel edges
      3. loop
6. parameters of graph
   1. size
   2. order
7. special families of graph
   1. complete graph
   2. empty graph
   3. bipartite
      1. complete bipartite graph
   4. path
   5. circle