  These lecture notes for the IAS/Park City Graduate Summer School in Geometric
Combinatorics (July 2004) provide an overview of root systems, generalized
associahedra, and the combinatorics of clusters.
  Lectures 1-2 cover classical material: root systems, finite reflection
groups, and the Cartan-Killing classification. Lectures 3-4 provide an
introduction to cluster algebras from a combinatorial perspective. Lecture 5 is
devoted to related topics in enumerative combinatorics.
