This system of analysis is called stratificational because it is based upon the notion that every language comprises a restricted number of structural layers or strata, hierarchically related in such a way that units or combinations of units on one stratum realize units or combinations of units of the next higher stratum. The number of strata may vary from language to language. Four strata have been recognized for English, and it is probable that all languages may have at least these four: the sememic, the lexemic, the morphemic, and the phonemic strata. The sememic stratal system constitutes the semology of the language; the lexemic and morphemic stratal systems constitute the grammar (in the narrower sense of this term); and the phonemic system constitutes the phonology. In some later stratificational work, the term grammar covers the three higher stratal systems—the sememic, the lexemic, and the morphemic—and is opposed to “phonology.” The deep structure of sentences is described on the sememic stratum and the surface structure on the morphemic. In the present account, “grammar” is used in the narrower sense and will be opposed to “semology” as well as “phonology.”
The originality of stratificational grammar does not reside in the recognition of these three major components of a linguistic description. The stratificational approach to linguistic description is distinguished from others in that it relates grammar to semology and phonology by means of the same notion of realization that it employs to relate the lexemic and the morphemic stratal systems within the grammatical component. Another distinguishing feature of stratificational grammar, in its later development at least, is its description of linguistic structure in terms of a network of relationships, rather than by means of a system of rules; linguistic units are said to be nothing more than points, or positions, in the relational network.
This is an excerpt from Encyclopedia Britannica that offers a very general overview of the discipline of Linguistics.
