Indegree

The number of edges that point to the vertex.

Outdegree

The number of outgoing edges from the vertex.

Reverse graph

A graph with the same vertices but the edges are reversed.

Undirected graph

Undirected graphs have edges that do not have a direction. The edges indicate a two-way relationship, in that each edge can be traversed in both directions.

Connected graph

A graph is said to be connected if every pair of vertices in the graph is connected. This means that there is a path between every pair of vertices.