Generative grammar is a linguistic theory that considers grammar to be a system of rules that is intended to generate exactly those combinations of words which form grammatical sentences in a given language. The term was originally used in relation to the theories of grammar developed by Noam Chomsky, beginning in the late 1950s. Linguists who follow the generative approach, originated by Chomsky, have been called generativists. The generative school has focused on the study of syntax, but has also addressed other aspects of a language's structure, including morphology and phonology.