# Graph Theory Primer

*Basic concepts & examples in an academic style*

**Graphs and Variants**: A graph is a set of *nodes*. Some pairs of nodes are connected by *edges*. A graph is *directed* if its edges are oriented. Directed edges are called *arcs*. A graph is *weighted* if its nodes or edges have numeric weights on them. A graph is called a *multigraph* if a pair of nodes may be connected by multiple edges.

Underlying a directed graph is an undirected graph obtained by stripping away the directions of the arcs and removing any duplicate edges that might result.