6.1 Constituents and phrase structure rules

Sentences are like building blocks, each part playing a crucial role. We'll explore how words group together to form meaningful units called constituents. These can be moved, replaced, or joined in various ways to create different sentence structures.

Understanding sentence structure helps us communicate more effectively. We'll look at phrase structure rules, the relationships between heads and dependents, and how constituents fulfill different roles in sentences. This knowledge forms the foundation for clear and precise language use.

Sentence Structure and Constituents

Constituents in sentences

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• Constituents function as single units within sentences grouped together (noun phrases, verb phrases)
• Constituency tests identify constituents:
  • Replacement substitutes constituent with pronoun or simple word (The big red ball → It)
  • Movement shifts constituent to different position (On the table, I placed the book)
  • Cleft places constituent in "It is/was ... that" structure (It was the red car that I bought)
  • Coordination joins similar constituents with coordinating conjunction (I like [apples and oranges])
• Common constituents include:
  • Noun phrases express entities or concepts (The tall building)
  • Verb phrases describe actions or states (is running quickly)
  • Prepositional phrases indicate relationships (under the bridge)
  • Adjective phrases modify nouns (extremely happy)
  • Adverb phrases modify verbs, adjectives, or other adverbs (very quickly)

Phrase structure rules

• Phrase structure rules represent sentence and phrase construction formally (Category → Constituent(s))
• Basic rules outline fundamental sentence structures:
  • S → NP VP (Sentence consists of noun phrase and verb phrase)
  • NP → (Det) (Adj) N (PP) (Noun phrase may include determiner, adjective, noun, prepositional phrase)
  • VP → V (NP) (PP) (Verb phrase includes verb, optional noun phrase and prepositional phrase)
  • PP → P NP (Prepositional phrase contains preposition and noun phrase)
• Recursive rules allow phrase embedding (NP → NP PP) enables complex structures (The book [on the shelf] [in the library])
• Tree diagrams visually represent phrase structure hierarchies showing relationships between constituents

Heads vs dependents

• Heads determine phrase's syntactic category (noun in noun phrase, verb in verb phrase)
• Dependents modify or complement the head:
  • Complements required by head (give [the book] to John)
  • Adjuncts optionally modify (eat [quickly])
• X-bar theory organizes phrase structure:
  • Intermediate projection (X') combines head with complement
  • Maximal projection (XP) includes specifier and adjuncts
  • Positions: Specifier (subject), complement (object), adjunct (modifier)

Constituents and sentence roles

• Grammatical functions define constituent roles (subject, predicate, object, complement, modifier)
• Thematic roles describe semantic relationships (agent performs action, patient affected by action)
• Constituent order in English follows SVO pattern (Subject-Verb-Object)
• Subcategorization specifies verb requirements for constituents (transitive verbs require objects, intransitive do not)
• Structural ambiguity arises from multiple possible interpretations ("The man saw the girl with the telescope" - man or girl has telescope?)