Transformational grammar, is a system for converting a deep structure into a surface structure.

Transformational Grammar

A theory of grammar that considers the syntactic structures of language as being generated by a set of rules.

Deep Structure

In linguistics, the underlying syntactic structure or meaning of a sentence, as opposed to the surface structure which is how the sentence is expressed verbally.

Surface Structure

In linguistics, the term refers to the outward form of a sentence, which can vary without altering its deep structure or meaning.