Basic Facts -- Closed Subsets -- Generating Subsets -- Quotient Schemes -- Morphisms -- Faithful Maps -- Products -- From Thin Schemes to Modules -- Scheme Rings -- Dihedral Closed Subsets -- Coxeter Sets -- Spherical Coxeter Sets.The present text is an introduction to the theory of association schemes. We start with the de?nition of an association scheme (or a scheme as we shall say brie?y), a…