In the book Outline of Stratification Grammar, he states that language is a system of several related layers, strata of structure. In stratification grammar, language is envisaged and analyzed in terms of a number of different strata. Each layer has its own rules of formation and is related to each other. In 1972, D.G. Lockwood wrote Introduction to Stratification Linguistics.
Ethnic stratification is another interesting use of stratification.
In the February 1900 volume of the Quarterly Journal for Economics, John Cummings of Harvard University discussed the way anthropologists have done away with ethnic stratification, a system based on naive classifications of mankind into white, black, yellow, red, and brown races. 31 May 2000. A Dictionary of Linguistics and Phonetics. E.S.C. The Oxford English Dictionary.