Glossary of Literary Theory by Greig E. Henderson and Christopher Brown

Deep structure:

A term used by Noam Chomsky, who argues that grammatically well-formed utterances in a language conceal a bipartite structure consisting, on the one hand, of a visible or "surface structure" -- the structure of the actual sentence uttered -- and, on the other hand, of a "deep structure" or "base component" -- the paradigm underlying it. According to Chomsky, every language has a core structure comprehending a set of generating principles which allows certain syntactic transformations, and these are to be analyzed as independent of particular meanings. Hence the idea of generative or transformational grammar, which focuses on the laws of transformation within the realm of deep structure and assumes the priority of syntax over semantics, structure over use. (See also Linguistics and literary theory, Surface structure.)