CentralNotice Colorless green ideas sleep furiously From Wikipedia, the free encyclopedia Jump to: navigation , search Approximate X-Bar representation of "Colorless green ideas sleep furiously." See phrase structure rules . "Colorless green ideas sleep furiously" is a sentence composed by Noam Chomsky in his 1957 Syntactic Structures as an example of a sentence that is grammatically correct, but semantically nonsensical . The term was originally used in his 1955 thesis "Logical Structures of Linguistic Theory" and in his 1956 paper "Three Models for the Description of Language". [ 1 ] Although the sentence is grammatically correct, no obvious understandable meaning can be derived from it, and thus it demonstrates the distinction between syntax and semantics . As an example of a category mistake , it was used to show inadequacy of the then-popular probabilistic mode...