transformational grammar

Theory of language structure initiated by the US linguist Noam Chomsky, which proposes that below the actual phrases and sentences of a language (its surface structure) there lies a more basic layer (its deep structure), which is processed by various transformational rules when we speak and write.

Below the surface structure ‘the girl opened the door’ would lie the deep structure ‘the girl open + (past tense) the door’. Note that there is usually more than one way in which a deep structure can be realized; in this case, ‘the door was opened by the girl’.