Words group into intermediate units before they form full clauses. A phrase is a group of words that functions as a single constituent, built around a head such as a noun, verb, adjective, or preposition.

Noun phrases, verb phrases, and prepositional phrases are familiar examples. Phrases can contain other phrases, creating hierarchical structure. Constituency tests—movement, replacement, and coordination—help identify phrase boundaries.

Phrase structure is a core topic in syntax teaching and parsing algorithms. Misplaced phrase boundaries cause ambiguity, as in classic garden-path sentences. Understanding phrases lets writers and analysts explain why certain word sequences behave as units.

• Syntactic unit built around a head word
• Includes noun, verb, and prepositional phrases
• Can embed other phrases hierarchically
• Identified by constituency tests