What is a context-free grammar, and why are parameters used in it?

A context‑free grammar (CFG) is a formal grammar where each production rule has a single nonterminal on the left‑hand side and a string of terminals and/or nonterminals on the right. CFGs are used to describe the syntax of programming languages. Parameters, often represented by nonterminals, allow the grammar to be modular and recursive, enabling the definition of complex constructs. In parser generators, parameterized rules let you reuse patterns with different arguments, improving maintainability and clarity. The use of parameters also supports context‑free properties, ensuring that the production rules do not depend on surrounding symbols.