Chomsky hierarchy

Chomsky is famous for investigating various kinds of formal languages and whether or not they might be capable of capturing key properties of human language. His Chomsky hierarchy partitions formal grammars into classes, or groups, with increasing expressive power, i.e., each successive class can generate a broader set of formal languages than the one before. Interestingly, Chomsky argues that modeling some aspects of human language requires a more complex formal grammar (as measured by the Chomsky hierarchy) than modeling others. For example, while a regular language is powerful enough to model English morphology, it is not powerful enough to model English syntax. In addition to being relevant in linguistics, the Chomsky hierarchy has also become important in computer science(especially in compiler construction and automata theory).