 Formal grammar

A grammar $(N,\Sigma ,P,S)$ generates the terminal words reachable from $S$ by finitely many productions.

Formal grammar is a set of rules and structures that define the syntax of a language. It provides a formal way to describe how sentences or expressions in a language can be constructed. Formal grammars are widely used in computer science, linguistics, and artificial intelligence to define programming languages, natural languages, and various systems of communication.