What is Chomsky Hierarchy? Noam Chomsky categorised regular and other languages which called as Chomsky Hierarchy. Language Class Grammar Automaton 3 Regular NFA or DFA 2 Context-Free Push-Down Automaton 1 Context-Sensitive Linear-Bounded Automaton 0 Unrestricted (or Free) Turing Machine This is a hierarchy, so every language of type 3 is also of types 2, 1 and 0; every language of type 2 is also of types 1 and 0