BNF

Computer science

• Backus–Naur Form, a formal grammar for expressing context-free grammars

Biology and medicine

• British National Formulary, the standard drug reference manual
• British National Formulary for Children
• British Nutrition Foundation

Literature

• Big Name Fan
• BnF or the Bibliothèque nationale de France, the French National Library in Paris.

Politics

• Parties associated with the Belarusian People's Front are also known as BNF:
• Belarusian People's Front
• Conservative Christian Party of the Belarusian People's Front
• Botswana National Front
• British National Front, a far-right political party in the United Kingdom.

Business

• British Nuclear Fuels, or more properly, BNFL.
• B.N.F , a mass media christened alias for a famous Japanese internet trader.