A cluster variable is any element appearing in a cluster obtained from the initial seed of a cluster algebra by a sequence of seed mutations. Each cluster is an 
-tuple of algebraically
independent cluster variables, and the cluster algebra is generated by all of
its cluster variables.
Cluster Variable
See also
Cluster Algebra, Laurent Phenomenon, Seed MutationExplore with Wolfram|Alpha
References
Fomin, S. and Zelevinsky, A. "Cluster Algebras I: Foundations." J. Amer. Math. Soc. 15, 497-529, 2002. https://doi.org/10.1090/S0894-0347-01-00385-X.Cite this as:
Weisstein, Eric W. "Cluster Variable." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/ClusterVariable.html