constituency parsing

**Constituency Parsing** is a **syntactic analysis task that breaks a sentence into a hierarchy of nested phrases (constituents)** — representing structure as a tree where leaves are words and internal nodes are phrase types (NP: Noun Phrase, VP: Verb Phrase, PP: Prepositional Phrase). **Structure** - **Hierarchy**: Sentences are typically divided recursively: S $ o$ NP VP. - **Non-terminal nodes**: Abstract categories (NP, VP, S). - **Terminal nodes**: The actual words. - **Example**: "The black cat" $ o$ [NP [Det The] [Adj black] [N cat]]. **Why It Matters** - **Linguistics**: Aligns with Noam Chomsky's Transformational Grammar / Phrase Structure Grammar. - **Scope**: Useful for resolving scope ambiguity ("old men and women" — is "old" modifying just "men" or both?). - **Recursive Neural Networks**: Tree-structured networks (Tree-LSTMs) run over constituency trees. **Constituency Parsing** is **nested shelving** — organizing words into small phrases, which fit into larger phrases, forming a complete sentence structure.