# Understanding the Chomsky Hierarchy of Formal Grammars

Chomsky hierarchy - Wikipedia 🔗

The Chomsky hierarchy classifies formal grammars into four types, which generate increasingly complex languages. Proposed by Noam Chomsky, this hierarchy aids in understanding how different grammars correspond to various computational models. Each grammar type is defined by its production rules and the languages it can generate, from regular languages recognized by finite-state automata to recursively enumerable languages recognized by Turing machines. The hierarchy reveals the relationships between these language classes, illustrating that every regular language is context-free, and so forth, with proper inclusions among the types.

**Types of Grammars:****Type-3 (Regular):**Generates regular languages, recognized by finite-state automata.**Type-2 (Context-free):**Produces context-free languages, recognized by non-deterministic pushdown automata.**Type-1 (Context-sensitive):**Creates context-sensitive languages, recognized by linear-bounded non-deterministic Turing machines.**Type-0 (Recursively enumerable):**Includes all formal grammars, recognized by Turing machines.

### What is the Chomsky hierarchy?

The Chomsky hierarchy is a classification of formal grammars into four types, representing different levels of language complexity and their computational capabilities.

### How are the types of grammars related?

Each type of grammar can generate the languages of all inferior types, meaning that all regular languages are context-free, all context-free languages are context-sensitive, and so on.

### What are the practical applications of these grammars?

These grammars are crucial in fields like computer science and linguistics, helping to define the syntax of programming languages and to understand language processing by machines.