Recommended terminology for matrix R and metamerism

In recent years new terminology for metamerism and related phenomena has been put forth. Terms associated with these phenomena are presented in the form of recommendations from ISCC Committee #27: Indices of Metamerism. The terms are given with a definition and where appropriate a symbol is recommended. A subject closely allied to metamerism is Cohen and Kappauf's spectral decomposition theory, often referred to as Matrix R theory. Terms, symbols, and definitions associated with this subject are additionally recommended. The recommendations are made in the interest of uniformity of future practice on the part of writers and users.