 Specifically, pragmatics tends to focus on deictics—words and expressions of language that derive some part of their referential meaning from indexicality—since these are regarded as "[t]he single most obvious way in which the relationship between language and context is reflected in the structures of languages themselves" Indeed, in linguistics the terms "deixis" and "indexicality" are often treated as synonymous, the only distinction being that the former is more common in linguistics and the latter in philosophy of language.This usage stands in contrast with that of linguistic anthropology, which distinguishes deixis as a particular subclass of indexicality; see below.The concept of indexicality was introduced into the literature of linguistic anthropology by Michael Silverstein in a foundational 1976 paper, "Shifters, Linguistic Categories and Cultural Description".