Recursion

Grammar’s loop: clauses nest inside clauses, giving finite rules an unbounded number of sentences.

Core Principles & Analysis

• "The rat the cat the dog chased bit died" is grammatical — and nearly unparseable past two embeddings.
• Recursion lets a finite grammar generate infinitely many sentences, a point central to Chomsky’s program.
• Whether Pirahã lacks recursion became one of modern linguistics’ fiercest disputes.