Backus-Naur form - A formal metasyntax used to express context-free grammars. Backus Normal Form was renamed Backus-Naur Form at the suggestion of Donald Knuth.
BNF is one of the most commonly used metasyntactic notations for specifying the syntax of programming languages, command sets, and the like. It is widely used for language descriptions but seldom documented anywhere (how do you document a metasyntax?), so that it must usually be learned by osmosis (but see
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дс тдрлими цюлютдажкию дроемжки аиакиохдйис лидр
http://foldoc.doc.ic.ac.uk/foldoc/foldoc.cgi;