Coxeter groups, Hecke algebras and their representations.- Applications of Kazhdan-Lusztig theory.- Geometric interpretations of the Kazhdan-Lusztig polynomials.- The algebraic descriptions of the affine Weyl group An of type Ãn?1, n>2.- The partition of n associated with an element of the affine Weyl group An.- A geometrical description of the affine Weyl group An.- Admissible sign types of rank n.- Iterated star operations and interchanging operations on blocks.- The subset ??1(?) of the affine Weyl group An.- The set N ? of normalized elements of ??1(?).- The orbit space Ãn of the affine Weyl group An.- The sequence ?(w,k) beginning with an element of N ?.- Raising operations on layers.- The left and right cells in ??1(?).- ??1(?) is an rl-equivalence class of An.- Left cells are characterized by the generalized right ?-invariant.- The two-sided cells of the affine Weyl group An.- Some properties of cells and other equivalence classes of An.- Some special kinds of sign types.- The inserting algorithm on the set C.- The restriction of the map on p n.