bnf

• genelde programlama dilleri için kullanılsa da natural languages için de kullanılabilir.
  
  örneğin phrase structure grammer'ı g = (v, t, s, p) olan ingilizcenin alt kümesi bir dil düşünelim. sırasıyla vocabulary, terminal, starting symbol ve productions'ı aşağıdaki gibi tanımlı olsun:
  
  v = {(sentence), (noun phrase), (verb phrase), (article), (adjective), (noun), (verb),
  (adverb), a, the, large, hungry, rabbit, mathematician, eats, hops, quickly, wildly}
  
  t = {a, the, large, hungry, rabbit, mathematician, eats, hops, quickly, wildly}
  
  s = (sentence)
  
  p = { (sentence) › (noun phrase) (verb phrase),
  (noun phrase) › (article) (adjective) (noun),
  (noun phrase) › (article) (noun),
  (verb phrase) › (verb) (adverb),
  (verb phrase) › (verb),
  (article) › a,
  (article) › the,
  (adjective) › large,
  (adjective) › hungry,
  (noun) › rabbit,
  (noun) › mathematician,
  (verb) › eats,
  (verb) › hops,
  (adverb) › quickly,
  (adverb) › wildly }
  
  bu dilin backus-naur form (bnf)'u şu şekilde yazılır:
  
  <sentence> ::= <noun phrase> <verb phrase>
  <noun phrase> ::= <article> [<adjective>] <noun>
  <verb phrase> ::= <verb> [<adverb>]
  <article> ::= a | the
  <adjective> ::= large | hungry
  <noun> ::= rabbit | mathematician
  <verb> ::= eats | hops
  <adverb> ::= quickly | wildly