Graph Terminology

• Vertex (vertices) – A point on the graph. We have called these “nodes” in the past. Usually represented as letters or numbers in theory.

• Edge – A connection between to vertices. Represented by naming the two vertices. So (A,B) would be the edge between Vertex A and Vertex B.

• Set - A group of items that have no importance or order to them. So {A,B,C} is equivalent to {B,C,A} and {C,B,A} etc. The order doesn’t’ matter. They are just a group of items that share something in common.

• Cyclic – A directed graph which has at least one cycle. A cycle is where you can start at one vertex, and arrive back at that vertex through the graph. So A->B->C->A. This path starts at A, and ends at A.

• Ayclic – A directed graph which doesn’t have any cycles. Once you touch a vertex, there is no way to get back to that vertex.

• Connected – A graph in which each vertex is connected to together by some path. So from any node, one could follow the edges and make it to every other node.

• Disconnected – A graph in which every single vertex is not connected. This could be a single vertex by itself or a bunch of smaller connected graphs. The point is atleast one of these vertices are not connected with the rest.

• Adjacency(邻近距离) – When two vertices are connected to one another. So if we have the edge (A,B), A and B are adjacent to one another