rewrite rule

A type of RULE in GENERATIVE GRAMMAR, which takes the form X → Y; also called a rewriting rule. The symbol to the left of the arrow represents a single STRUCTURAL ELEMENT; the symbol to the right of the arrow represents a STRING of one or more elements: and the arrow is an instruction to replace (or ‘expand’) X by Y. Such rules are conventionally read as ‘Rewrite X as Y’; see further, PHRASE-STRUCTURE GRAMMAR, ENVIRONMENT.