1.3 Undirected Graph
If the edges of are unordered pairs, is a undirected graph. In an undirected graph, . If edge of an undirected graph is represented by , then is adjacent to and is adjacent to . The terminology “undirected graph” is somewhat cumbersome. In this document, undirected graphs are often referred to as just “graphs”.
Figure 2 depicts an undirected graph with six vertices and eight edges. The fact that the graph is undirected is indicated by the absence of directionality arrows.