Language is considered as a system primarily because it is made of linguistic units that are interdependent of each other. Since they are smaller units working within a whole system, by default, language becomes a system of systems. The basic premise of this concept is that the diversity of features that are found in language formation and production prevents it from being described in a diluted or generalized way. Instead, language study has to be pulled apart and studied by each of its multifunctional sub-systems.
The idea of language being a system of systems comes primarily from an article written by Mulder and Hervey (1975) and publishedLa Linguistique(11,(2)). Mulder and Hervey's definition of language follows a functionalist perspective in which language is defined as a "genus" and, as such, it should be subdivided into a smaller sub-parts, or systems.
Five sub-systems of language are identified as
- Semantics- Rules of language content. It has a sub-system of its own based on vocabulary and word localization.
- Pragmatics- Rules of language usage (function and appropriateness)
- Syntax- Rules for word order and arrangements
- Morphology- Rules for word formation. Also has its own sub-system of morphemes.
- Phonology- Rules for how the language sounds, or should sound.
Therefore, the complexity of language and the fact that it is a composite of various functional parts are the conditions that deem it, quite correctly, as a system of systems.