Metasyntax

Metasyntax is a notation or formal system for describing the syntax of another language. It makes grammatical rules explicit, as Backus–Naur form does for programming languages.

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Formal grammar: A mathematical system of rules that defines how strings in a language can be formed. Metasyntaxes encode formal grammars as readable or machine-processable notation.
Backus–Naur form: A notation for context-free grammars using named nonterminals and production rules. It is the best-known metasyntax for specifying programming-language grammars.
John Backus: An American computer scientist who led the development of Fortran and helped create Backus–Naur form. His work on describing Algol syntax gave the notation its name.
Compiler: A program that translates source code from one language into another representation or executable form. Compiler construction uses grammar descriptions to define and recognize source-language structure.
Production rule: A rule that specifies how a symbol or sequence can be replaced by another sequence. Production rules are the core statements that grammar notations express.
Extended Backus–Naur form: A family of extensions to Backus–Naur form that adds shorthand for repetition, optionality, and grouping. Its operators make common grammar patterns more compact than in basic BNF.
Peter Naur: A Danish computer scientist who edited the Algol 60 report and helped popularize Backus–Naur notation. Naur's grammar presentation in the Algol report made the notation widely influential.
Parser: A program or component that analyzes a sequence of tokens according to a grammar. A grammar written in metasyntax can guide parser construction.
Terminal symbol: A basic symbol of a grammar that appears directly in generated strings and is not expanded by grammar rules. Metasyntax distinguishes literal tokens from symbols that stand for grammatical parts.
Parsing expression grammar: A formal grammar for parsing with prioritized choice, yielding an unambiguous recognition procedure. Its ordered-choice semantics differ from the alternatives in ordinary context-free grammar notation.