Phrase structure rules
rewrite rule used to describe a given language's syntax, used to break down a natural language sentence into its syntactic categories (both lexical and phrasal); used in transformational grammar; first proposed by Noam Chomsky in 1957
Phrase structure rules are a type of rewrite rule used to describe a given language's syntax and are closely associated with the early stages of transformational grammar, proposed by Noam Chomsky in 1957. They are used to break down a natural language sentence into its constituent parts, also known as syntactic categories, including both lexical categories (parts of speech) and phrasal categories. A grammar that uses phrase structure rules is a type of phrase structure grammar. Phrase structure rules as they are commonly employed operate according to the constituency relation, and a grammar that employs phrase structure rules is therefore a constituency grammar; as such, it stands in contrast to dependency grammars, which are based on the dependency relation.
Definition and examples
Phrase structure rules are usually of the following form:
A
→
B
C
{\displaystyle A\to B\quad C}
meaning that the constituent
A
{\displaystyle A}
is separated into the two subconstituents
B
{\displaystyle B}
and
C
{\displaystyle C}
. Some examples for English are as follows:
S
⟶
NP
VP
{\displaystyle {\ce {S->NP\quad VP}}}
NP
⟶
(
Det
)
N
1
{\displaystyle {\ce {NP->(Det)\quad N1}}}
N
1
⟶
(
AP
)
N
1
(
PP
)
{\displaystyle {\ce {N1->(AP)\quad N1\quad (PP)}}}
The first rule reads: A S (sentence) consists of a NP (noun phrase) followed by a VP (verb phrase). The second rule reads: A noun phrase consists of an optional Det (determiner) followed by a N (noun). The third rule means that a N (noun) can be preceded by an optional AP (adjective phrase) and followed by an optional PP (prepositional phrase). The round brackets indicate optional constituents.
Beginning with the sentence symbol S, and applying the phrase structure rules successively, finally applying replacement rules to substitute actual words for the abstract symbols, it is possible to generate many proper sentences of English (or whichever language the rules are specified for).
Begin with the source’s own compact description: “Phrase structure rules” is rewrite rule used to describe a given language's syntax, used to break down a natural language sentence into its syntactic categories (both lexical and phrasal); used in transformational grammar; first proposed by Noam Chomsky in 1957. The dossier treats that line as a proposition to test through Phrase, structure and rules, not as a finished interpretation.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Apr 23, 2024. The linked authority identifier is Q7188074. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1957.
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