 For this reason, recursive definitions are very rare in everyday situations.Linguist Noam Chomsky, among many others, has argued that the lack of an upper bound on the number of grammatical sentences in a language, and the lack of an upper bound on grammatical sentence length (beyond practical constraints such as the time available to utter one), can be explained as the consequence of recursion in natural language.This can be understood in terms of a recursive definition of a syntactic category, such as a sentence.