The Symbolic Function and Communicative Function of Language
The Symbolic Function of language is the mechanism by which meaning is attached to form. It is the pairing of form and meaning; the symbolic function is a sense-making utility that labels objects (referents) with “names” that map to a conceptualized meaning.
The Communicative Function of language is the means by which parties exchange notions of combined symbols in conventionalized ways to share conceptualizations in a relational way. This includes the ability to alter states of the world, to express internalizations, and to situate meaning in ad hoc frames that draw on world knowledge and encyclopedic knowledge.
These two functions interact in a number of ways, actual usage of symbols to communicate being one of those interactions – this may work to explain how idioms form, as the symbols are used in communication to attach meaning to a symbolic construction – entrenched usage normalizing the idiomatic construction into a common unit of communication.
Evans, V. & Green, M. (2006). Cognitive Linguistics an Introduction, Lawrence Erlbaum Associates