Formal grammars come in a hierarchy of expressive power, first introduced by Noam Chomsky.

**Type-0 grammars**, also known as unrestricted grammars generate the recursively enumerable languages, they correspond to Turing machines.**Type-1 grammars**are also called context sensitive grammars, they correspond to linear-bounded nondeterministic Turing machines.**Type-2 grammars**are also called context free grammars, they correspond to nondeterministic pushdown automata.**Type-3 grammars**generate regular languages, they are equivalent to regular languages and finite-state automata.

Last revised on November 24, 2020 at 18:03:46. See the history of this page for a list of all contributions to it.