Phrase structure rules

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Phrase structure rules are rewrite rules that generate phrase structure(s). These have the general form of (i), where X is the name of the phrase and Y Z W defines its structure. Y, Z, and W are either phrases, and therefore must themselves occur to the left of the arrow in rules of this type, or non-phrasal (terminal) categories (such as Noun, Verb, or Determiner).

(i)     X	->	Y Z W ...


the phrase structure rules in (ii) generate the phrase structure of the sentences in (iii).

(ii)  a	 S	->	NP VP
      b	 VP	->	V(NP) (PP)
      c	 NP	->	(Det) N
      d	 PP	->	P NP

(Round Brackets indicate that a phrase is optional)

(iii) a	 John laughs
      b	 John eats an apple
      c	 The girl walks in the forest
      d	 The boy sends flowers to his mother

Thus the phrase structure rule in (ii)a characterizes a sentence (S) as the combination of an NP (the subject) and a VP (the predicate), i.e. as in (iv).

(iv)  a	 [S [NP[N John]] [VP[V laughs] ] ]
      b	 [S [NP[N John]] [VP[V eats][NP[Det an][N apple]] ] ]
      c	 [S [NP[Det the][N girl]]  [VP[V walks] [PP[P in]
         [NP[Det the][N forest]] ] ] ]
      d	 [S [NP[Det the][N boy]]  [VP[V sends] [NP[N flowers]]
         [PP[P to][NP[Det his] [N mother] ] ] ] ]

The phrase structure rule in (ii)b gives the internal structure of the VP. According to this rule, a verbal phrase consists of a verb and, optionally, an NP and a PP. These last two constituents are further defined in phrase structure rules (iic/d).

Originally (cf. Chomsky 1957, 1965), phrase structure rules were meant to generate Deep-structures, which are converted into Surface structures by transformational rules. With the introduction of the Principles and Parameters framework (Cf. Stowell 1981, Chomsky 1986a), phrase structure rules have been eliminated from the theory of language as descriptive generalizations of what is better explained by deeper principles. Another term for phrase structure rules is rewrite rules. Also see X-bar theory.


Utrecht Lexicon of Linguistics


  • Chomsky, N. 1986a. Knowledge of language: its nature, origin and use, Praeger, New York.
  • Chomsky, N. 1965. Aspects of the Theory of Syntax, MIT Press, Cambridge, MA.
  • Chomsky, N. 1957. Syntactic structures, Mouton, The Hague.
  • Riemsdijk, H. van and E. Williams 1986. Introduction to the theory of grammar, MIT Press, Cambridge, Mass.
  • Stowell, T. 1981. Origins of Phrase structure, Diss, MIT.