Definition of Deep Structure

In transformational and generative grammar, deep structure (also known as deep grammar or D-structure) is the underlying syntactic structure—or level—of a sentence. In contrast to surface structure (the outward form of a sentence), deep structure is an abstract representation that identifies the ways a sentence can be analyzed and interpreted. Deep structures are generated by phrase-structure rules, and surface structures are derived from deep structures by a series of transformations.

According to the "Oxford Dictionary of English Grammar" (2014):

"Deep and surface structure are often used as terms in a simple binary opposition, with the deep structure representing meaning, and the surface structure being the actual sentence we see."

The terms deep structure and surface structure were popularized in the 1960s and '70s by American linguist Noam Chomsky, who eventually discarded the concepts in his minimalist program in the 1990s. 

Properties of Deep Structure

"Deep structure is a level of syntactic representation with a number of properties that need not necessarily go together. Four important properties of deep structure are:

1. Major grammatical relations, such as subject of and object of, are defined at deep structure.
2. All lexical insertion occurs at deep structure.
3. All transformations occur after deep structure.
4. Semantic interpretation occurs at deep structure.

"The question of whether there is a single level of representation with these properties was the most debated question in generative grammar following the publication of "Aspects [of the Theory of Syntax" 1965]. One part of the debate focused on whether transformations preserve meaning."

– Alan Garnham, "Psycholinguistics: Central Topics." Psychology Press, 1985

Examples and Observations

"[Noam] Chomsky had identified a basic grammatical structure in Syntactic Structures [1957] that he referred to as kernel sentences. Reflecting mentalese, kernel sentences were where words and meaning first appeared in the complex cognitive process that resulted in an utterance. In [Aspects of the Theory of Syntax, 1965], Chomsky abandoned the notion of kernel sentences and identified the underlying constituents of sentences as deep structure. The deep structure was versatile insofar as it accounted for meaning and provided the basis for transformations that turned deep structure into surface structure, which represented what we actually hear or read. Transformation rules, therefore, connected deep structure and surface structure, meaning and syntax."

– James D. Williams, "The Teacher's Grammar Book." Lawrence Erlbaum, 1999

"[Deep structure is a] representation of the syntax of a sentence distinguished by varying criteria from its surface structure. E.g. in the surface structure of Children are hard to please, the subject is children and the infinitive to please is the complement of hard. But in its deep structure, as it was understood especially in the early 1970s, is hard would have as its subject a subordinate sentence in which children is the object of please: thus, in outline [please children] is hard."

– P.H. Matthews, "The Concise Oxford Dictionary of Linguistics." Oxford University Press, 2007

​Evolving Perspectives on Deep Structure

"The remarkable first chapter of Noam Chomsky's Aspects of the Theory of Syntax (1965) set the agenda for everything that has happened in generative linguistics since. Three theoretical pillars support the enterprise: mentalism, combinatoriality, and acquisition...

"A fourth major point of Aspects, and the one that attracted most attention from the wider public, concerned the notion of Deep Structure. A basic claim of the 1965 version of generative grammar was that in addition to the surface form of sentences (the form we hear), there is another level of syntactic structure, called Deep Structure, which expresses underlying syntactic regularities of sentences. For instance, a passive sentence like (1a) was claimed to have a Deep Structure in which the noun phrases are in the order of the corresponding active (1b):

• (1a) The bear was chased by the lion.
• (1b) The lion chased the bear.

"Similarly, a question such as (2a) was claimed to have a Deep Structure closely resembling that of the corresponding declarative (2b):

• (2a) Which martini did Harry drink?
• (2b) Harry drank that martini.

"...Following a hypothesis first proposed by Katz and Postal (1964), Aspects made the striking claim that the relevant level of syntax for determining meaning is Deep Structure.

"In its weakest version, this claim was only that regularities of meaning are most directly encoded in Deep Structure, and this can be seen in (1) and (2). However, the claim was sometimes taken to imply much more: that Deep Structure is meaning, an interpretation that Chomsky did not at first discourage. And this was the part of generative linguistics that got everyone really excited—for if the techniques of transformational grammar could lead us to meaning, we would be in a position to uncover the nature of human thought...

"When the dust of the ensuing 'linguistic wars' cleared around 1973 . . ., Chomsky had won (as usual)—but with a twist: he no longer claimed that Deep Structure was the sole level that determines meaning (Chomsky 1972). Then, with the battle over, he turned his attention, not to meaning, but to relatively technical constraints on movement transformations (e.g. Chomsky 1973, 1977)."

– Ray Jackendoff, "Language, Consciousness, Culture: Essays on Mental Structure." MIT Press, 2007

Surface Structure and Deep Structure in a Sentence

"[Consider] the final sentence of [Joseph Conrad's short story] 'The Secret Sharer':

Walking to the taffrail, I was in time to make out, on the very edge of a darkness thrown by a towering black mass like the very gateway of Erebus—yes, I was in time to catch an evanescent glimpse of my white hat left behind to mark the spot where the secret sharer of my cabin and of my thoughts, as though he were my second self, had lowered himself into the water to take his punishment: a free man, a proud swimmer striking out for a new destiny.

I hope others will agree that the sentence justly represents its author: that it portrays a mind energetically stretching to subdue a dazzling experience outside the self, in a way that has innumerable counterparts elsewhere. How does scrutiny of the deep structure support this intuition? First, notice a matter of emphasis, of rhetoric. The matrix sentence, which lends a surface form to the whole, is '# S # I was in time # S #' (repeated twice). The embedded sentences that complete it are 'I walked to the taffrail,' 'I made out + NP,' and 'I caught + NP.' The point of departure, then, is the narrator himself: where he was, what he did, what he saw. But a glance at the deep structure will explain why one feels a quite different emphasis in the sentence as a whole: seven of the embedded sentences have 'sharer' as grammatical subjects; in another three the subject is a noun linked to 'sharer' by the copula; in two 'sharer' is direct object; and in two more 'share' is the verb. Thus thirteen sentences go to the semantic development of 'sharer' as follows:

1. The secret sharer had lowered the secret sharer into the water.
2. The secret sharer took his punishment.
3. The secret sharer swam.
4. The secret sharer was a swimmer.
5. The swimmer was proud.
6. The swimmer struck out for a new destiny.
7. The secret sharer was a man.
8. The man was free.
9. The secret sharer was my secret self.
10. The secret sharer had (it).
11. (Someone) punished the secret sharer.
12. (Someone) shared my cabin.
13. (Someone) shared my thoughts.

"In a fundamental way, the sentence is mainly about Leggatt, although the surface structure indicates otherwise...

"[The] progression in the deep structure rather precisely mirrors both the rhetorical movement of the sentence from the narrator to Leggatt via the hat that links them, and the thematic effect of the sentence, which is to transfer Leggatt's experience to the narrator via the narrator's vicarious and actual participation in it. Here I shall leave this abbreviated rhetorical analysis, with a cautionary word: I do not mean to suggest that only an examination of deep structure reveals Conrad's skillful emphasis—on the contrary, such an examination supports and in a sense explains what any careful reader of the story notices."

– Richard M. Ohmann, "Literature as Sentences." College English, 1966. Reprinted in "Essays in Stylistic Analysis," ed. by Howard S. Babb. Harcourt, 1972