bipatite graph

http://encyclopedia.thefreedictionary.com/Bipartite%20graph

A bipartite graph is any graph whose vertices can be divided into two sets, such that there are no edges between vertices of the same set. A graph can be proved bipartite if there do not exist any circuits of odd length.

A k-partite graph or k-colorable graph is a graph whose vertices can be partitioned into k disjoint subsets such that there are no edges between vertices in the same subset. A 2-partite graph is the same as a bipartite graph.

http://www.utm.edu/departments/math/graph/glossary.html