This lesson was designed as an introduction to graph theory. I used it with my Discrete Mathematics class. It goes over how graphs are used to indicate connections, like computer links or social connections. Students will learn about vertex sets, edge sets, loops, parallel edges, isolated vertices, degrees of a vertex, connected vs. disconnected graphs, and more. The practice problem handout can be used to determine students' mastery of the lesson. It contains a set of 30 problems that ask stud