Noam Chomsky coined and popularized the term “deep structure”. Deep structure and surface structure are the complementary concepts upon which his Transformational Grammar is based.
According to this still disputed theory, all statements have two structures: a visible surface structure and a deep structure underlying it. The deep structure of a linguistic expression is a theoretical construct that seeks to unify several related structures. Deep structure is an abstract representation that identifies the ways a sentence can be analyzed and interpreted. The deep structure can usually be transformed into several surface structures. For example, the sentences “Charles bought a book” and “A book was bought by Charles” means roughly the same thing and use similar words. There is another example of the deep structure from Shakespeare’s line ‘That time of year thou may’st in me behold’ could be transformed into a variety of alternatives: “Thou may’st behold that time of year in me’, ‘In me thou may’st behold that time of year’, ‘That time of year in me thou may’st behold’, and so on.
Literary critics and theorists have broadened the application of the term to such an extent that their use of it should be understood figuratively. Thus, it is possible to say that the two novels of Jane Austen have the same deep structure. This would imply that they share the same basic plot, or a common theme, or the same set of closely related issues.