In formal language theory, a grammar is in Kuroda normal form if, and only if, all production rules are of the form:
where A, B, C and D are nonterminal symbols and α is a terminal symbol.
Every grammar in Kuroda normal form is monotonic, and therefore, generates a context-sensitive language. Conversely, every context-sensitive language which does not generate the empty string can be generated by a grammar in Kuroda normal form.
It is named for linguist S.-Y. Kuroda.