Bipartite graphs

undirected, connected and acyclic graph

graph whose vertices can be divided into two disjoint and independent sets

theorem showing that maximum matching and minimum vertex cover are equivalent for bipartite graphs

intrinsic property of undirected graphs

thumb|A squaregraph. In graph theory, a branch of mathematics, a squaregraph is a type of undirected graph that can be drawn in the plane in such a way that every bounded face is a quadrilateral and every vertex with three or fewer neighbors is incident to an unbounded face.

graph with a unique median for each three vertices