- a rule of transformational grammar that relates two phrase markers in the course of a derivation from the deep to the surface syntactic representation of a sentence, as by reordering, inserting, or deleting elements; a rule that converts deep structures into surface structures.
- a rule that converts one phrase marker into another. Taken together, these rules, which form the transformational component of the grammar, convert the deep structures of sentences into their surface structures
- a rule that specifies in purely syntactic terms a method by which theorems may be derived from the axioms of a formal system
