Roman Jakobson was a Russian thinker who became one of the most influential linguists of the 20th century by pioneering the development of the structural analysis of language, poetry, and art.
The linguistics of the time was overwhelmingly neogrammarian and insisted that the only scientific study of language was to study the history and development of words across time.
Jakobson, on the other hand, had come into contact with the work of Ferdinand de Saussure, and developed an approach focused on the way in which language structure served its basic function - to communicate information between speakers.
He was one of the founders of the "Prague school" of linguistic theory.
According to Jakobson, language must be investigated in all the variety of its functions.
An outline of those functions demands a concise survey of the constitutive factors in any speech event, in any act of verbal communication.
The ADDRESSER [speaker, author] sends a MESSAGE [the verbal act, the signifier] to the ADDRESSEE [the hearer or reader].
To be operative the message requires a CONTEXT [a referent, the signified], seizable by the addresses, and either verbal or capable of being verbalized;
a CODE [shared mode of discourse, shared language] fully, or at least partially, common to the addresser and the addressee (in other words, to the encoder and decoder of the message);
and, finally, a CONTACT, a physical channel and psychological connection between the addresser and the addressee, enabling both of them to enter and stay in communication.
Thus Jakobson distinguishes six communication functions, each associated with a dimension of the communication process:
3 sender --------------- 4 receiver
1 referential (= contextual information)
2 aesthetic (= auto-reflection)
3 emotive (= self-expression)
4 conative (= vocative or imperative addressing of receiver)
5 phatic (= checking channel working)
6 metalingual (= checking code working)
Jakobson's three main ideas in linguistics play a major role in the field to this day: linguistic typology, markedness and linguistic universals.
The three concepts are tightly intertwined:
typology is the classification of languages in terms of shared grammatical features (as opposed to shared origin)
markedness is (roughly) a study of how certain forms of grammatical organization are more "natural" than others, and
linguistic universals is the study of the general features of languages in the world.
See also: Roman Jakobson – On Linguistic Aspects of Translation - summary