| DefinitionsDefinitions Associated With Directed Graphs
				Digraphs are especially important in networking, where the main
				objects are collections of nodes with one-way links between them.
				 
				Many definitions from undirected
				graph theory have digraph-analogues:
				 
					The out-degree of a vertex
					 is the number of edges  for all  .
					The in-degree of a vertex
					 is the number of edges  for all  .
					Recall that in undirected graphs, a walk from vertex
					 to a vertex  is an
					alternating finite sequence of vertices and edges  such that  either  or  .
					In directed graphs, a directed walk from vertex
					 to a vertex  is an
					alternating finite sequence of vertices and edges  such that  .
					A directed path is a directed walk which does not
					repeat any vertex.
					
					A directed cycle is a directed walk which does
					not repeat any vertex except for the first and the last.
					
 | 
					A good glossary of graph-theoretical definitions can be found here.
					 | 
 |