Backus-Naur form UK /bækəs naʊə fɔːm/US /bækəs naʊɚ fɔɹm/ noun1 •A formal notation for context-free grammars.Here, a Backus-Naur Form (BNF) grammar is specified that allows a computer program or model to be constructed by a simple genetic algorithm operating on an array of bits. — 2004 formsBackus-Naur forms