In formal language theory, a grammar

Formal grammar

A formal grammar is a set of formation rules for strings in a formal language. The rules describe how to form strings from the language's alphabet that are valid according to the language's syntax...

 is in Kuroda normal form if, and only if, all production rules are of the form:

AB → CD or

A → BC or

A → B

A → α

where A, B, C and D are nonterminal symbols and α is a terminal symbol.

Every grammar in Kuroda normal form is monotonic

Noncontracting grammar

- Formal definition :In formal language theory, a grammar is noncontracting if all of its production rules are of the formThat is, none of the rules decreases the size of the string that is being rewritten....

, and therefore, generates a context-sensitive language

Context-sensitive language

In theoretical computer science, a context-sensitive language is a formal language that can be defined by a context-sensitive grammar. That is one of the four types of grammars in the Chomsky hierarchy...

. Conversely, every context-sensitive language which does not generate the empty string

Empty string

In computer science and formal language theory, the empty string is the unique string of length zero. It is denoted with λ or sometimes Λ or ε....

 can be generated by a grammar in Kuroda normal form.

It is named for linguist

Linguistics

Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

 S.-Y. Kuroda

S.-Y. Kuroda

, aka S.-Y. Kuroda, was Professor Emeritusand Research Professor of Linguistics at the University of California, San Diego.Although a pioneer in the application of Chomskyan generative syntax to...

.