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Graph theory is the branch of mathematics that examines the properties of mathematical graphs. See glossary of graph theory for common terms and their definition.

Informally, this type of graph is a set of objects called vertices (or nodes) connected by links called edges (or arcs), which can also have associated directions. Typically, a graph is depicted as a set of dots (i.e., vertices) connected by lines (i.e., edges), with an arrowhead on a line representing a directed arc.

Such graphs can be used to represent and analyze a variety of systems and problems, including colorability problems, shortest path algorithms and spanning trees.

For information on other types of graphs see graph (disambiguation).