In semiotics, linguistics, anthropology, and philosophy of language, indexicality is the phenomenon of a sign pointing to (or indexing) some object in the context in which it occurs. A sign that signifies indexically is called an index or, in philosophy, an indexical. The modern concept originates in the semiotic theory of Charles Sanders Peirce, in which indexicality is one of the three fundamental sign modalities by which a sign relates to its referent (the others being iconicity and symbolism). Peirce's concept has been adopted and extended by several twentieth-century academic traditions, including those of linguistic pragmatics, linguistic anthropology, and Anglo-American philosophy of language. Words and expressions in language often derive some part of their referential meaning from indexicality. For example, I indexically refers to the entity that is speaking; now indexically refers to a time frame including the moment at which the word is spoken; and here indexically refers to a locational frame including the place where the word is spoken. Linguistic expressions that refer indexically are known as deictics, which thus form a particular subclass of indexical signs, though there is some terminological variation among scholarly traditions. Linguistic signs may also derive nonreferential meaning from indexicality, for example when features of a speaker's register indexically signal their social class. Nonlinguistic signs may also display indexicality: for example, a pointing index finger may index (without referring to) some object in the direction of the line implied by the orientation of the finger, and smoke may index the presence of a fire. In linguistics and philosophy of language, the study of indexicality tends to focus specifically on deixis, while in semiotics and anthropology equal attention is generally given to nonreferential indexicality, including altogether nonlinguistic indexicality. In linguistic pragmatics In disciplinary linguistics, indexicality is studied in the subdiscipline of pragmatics. 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. In linguistic anthropology The concept