The concept of indexicality has been greatly elaborated in the literature of linguistic anthropology since its introduction by Silverstein, but Silverstein himself adopted the term from the theory of sign phenomena, or semiotics, of Charles Sanders Peirce. As an implication of his general metaphysical theory of the three universal categories, Peirce proposed a model of the sign as a triadic relationship: a sign is "something which stands to somebody for something in some respect or capacity." Thus, more technically, a sign consists of