The Backus-Naur form or Backus normal form (BNF) is a metasyntax notation for context-free grammars. Computer scientists often use this notation to describe the syntax of programming languages because it allows them to write a detailed description of a language's grammar.
The BNF notation consists of three core pieces: terminals, nonterminals, and rules.
For example, the Python syntax has a grammar that's defined as a set of BNF rules, and these rules are used to validate the syntax of any piece of Python code.
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