# Graph theory |  | In mathematics, **Graph theory** is the study of graphs, which are mathematical structures used to model pairwise relations between objects. A graph in this context is made up of vertices which are connected by edges. A distinction is made between undirected graphs, where edges link two vertices symmetrically, and directed graphs, where edges link two vertices asymmetrically. Graphs are one of the principal objects of study in discrete mathematics. | |-|-| | | wikipedia:: [Graph theory](https://en.wikipedia.org/wiki/Graph_theory) | [[Directed graph]] [[Topology]] [[Eulerian path]] [[Seven bridges of Konigsberg]] [[Leonhard Euler]] Routing problems like [[Travelling salesman problem]]