Chomsky hierarchy

A label applied to the series of increasingly powerful classes of FORMAL languages which can be generated by formal GRAMMARS (as first demonstrated by Noam Chomsky, using notions partly derived from AUTOMATA theory). Type 3 grammars are FINITE-STATE GRAMMARS (also called ‘right-linear grammars’); Type 2 grammars are CONTEXT-free grammars; Type 1 grammars are context-sensitive grammars; and Type 0 grammars are unrestricted REWRITE grammars.