The term phrase structure grammar was originally introduced by
Noam Chomsky as the term for
grammar
In linguistics, the grammar of a natural language is its set of structure, structural constraints on speakers' or writers' composition of clause (linguistics), clauses, phrases, and words. The term can also refer to the study of such constraint ...
studied previously by
Emil Post and
Axel Thue (
Post canonical systems). Some authors, however, reserve the term for more restricted grammars in the
Chomsky hierarchy:
context-sensitive grammars or
context-free grammars. In a broader sense, phrase structure grammars are also known as ''constituency grammars''. The defining trait of phrase structure grammars is thus their adherence to the constituency relation, as opposed to the dependency relation of
dependency grammar
Dependency grammar (DG) is a class of modern grammatical theories that are all based on the dependency relation (as opposed to the ''constituency relation'' of phrase structure) and that can be traced back primarily to the work of Lucien Tesni� ...
s.
Constituency relation
In
linguistics
Linguistics is the scientific study of human language. It is called a scientific study because it entails a comprehensive, systematic, objective, and precise analysis of all aspects of language, particularly its nature and structure. Lingu ...
, phrase structure grammars are all those grammars that are based on the constituency relation, as opposed to the dependency relation associated with dependency grammars; hence, phrase structure grammars are also known as constituency grammars. Any of several related theories for the
parsing of natural language qualify as constituency grammars, and most of them have been developed from Chomsky's work, including
*
Government and binding theory
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Generalized phrase structure grammar
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