# X-bar theory

The X-bar theory or X-bar syntax is a component of the linguistic theory of generative grammar , which makes statements about the sentence structure of natural languages. Its basic idea is that all natural languages are subject to common building principles: Every sentence is made up of constituents , so-called phrases. Every phrase, regardless of the language, always has a head X and can have complements or adjuncts, whereby the variable X stands for a word from the word classes noun , verb , adjective or preposition and complements and adjuncts are additions to the head. So is z. B. a verb phrase made up of a verb as a head (e.g. to give ) and objects as the associated extensions (e.g. to give the woman a book ). According to the X-bar theory, this structure of head and extensions is independent of part of speech and language. The X-bar theory was first formulated by Noam Chomsky in the 1970s and was further expanded in the further developments of generative grammar such as the rule and attachment theory .

## Basic idea

Illustration of the X-bar scheme in a tree diagram

According to the X-bar theory, all natural languages ​​are made up of phrases that are hierarchically structured. The constraints that this structure must meet are called the X-bar scheme . The X-bar scheme is illustrated in the form of a tree structure; it shows the maximum expansion of a phrase (apart from the fact that several adjuncts are possible). Not all available positions have to be used in individual cases.

For example, a noun phrase such as “large amounts of water” contains a so-called phrase head - here the word “amounts”. This is combined with the addition “von Wasser” and modified with the adjective “large”. In terms of the X-bar theory, the phrase head (X) “sets” requires the complement “of water” and has the adjective “large” as an adjunct . The specifier position has not been filled in this example. Since the expression "large amounts of water" already has all the necessary additions, it is called a phrase or also as the maximum projection of the head (noted as X ", so in the above example as N"): [large A " [amounts N ] [of water P " ]]

The position of the specifier, adjunct and complement on the left or right branch of a branch is left open by the X-bar theory - the arrangement shown in the diagram opposite is a special case, e.g. B. for the German noun phrase applies (i.e. with X = N).

In addition to specifying the syntactic hierarchy and the word order, the X-Bar scheme also plays a role in the administration of grammatical features. Phrase header and maximum sentences share a number of characteristics, which therefore also head characteristics are called. In the example, the head and the verb phrase V "include the attribute [+ past].

## Naming and spelling

The variable "X" in the term X-bar theory stands for the head in the phrase. The other part of the term "X-bar" theory is the English word bar for "bar" and comes from the fact that the extended projection of a head X was initially noted with a crossbar above the category symbol (ie ). Because of the difficulty of typing this notation, an apostrophe is used instead; these two notations are equivalent. ${\ displaystyle {\ bar {X}}}$

## X-bar scheme

The core of the X-bar theory, the so-called X-bar scheme, can be formulated in a recursive version as follows:

1. X ′ → {X, P ″}
2. X ′ → {X ′, P ″}
3. X ″ → {X ′, (P ″)}

X stands for the head of the phrase. Rule 1 says that a phrase head X together with a further maximum phrase P ″, which is required by X, form a unit ( constituent ) X ′. X ′ and X have the same head features. P ″ can either be mandatory, in which case it is called a complement . Rule 2 recursively allows further phrases P ″. These can be either mandatory or optional. If they are optional, they are called adjuncts . Finally, rule 3 allows the formation of a maximum unit X ″ (the phrase ) from the intermediate level X ′ and a further phrase P ″, which however can also be missing (indicated by round brackets). P ″ means specifier or specifier .

The set notation in rules 1) to 3) is intended to make it clear that the sequence of X or X ′ and P ″ is in principle left open, so the phrase head can appear before its argument as well as after it. Depending on the definitions in the grammar of an individual language, the rule scheme then generates, among other things, the tree shown above and other arrangements.

With the X-bar scheme you can e.g. B. generate the following phrases:

• Verb phrases: [abandon V [the investigation N " ] [after lunch P" ]] (Eng. [[Abandon the investigation] [after lunch]] )
• Noun phrases: [the Det [detective N ] [with the funny accent P " ]] (Eng. The detective with the funny accent )
• Adjective phrases: [conscious A [of the problem- P " ]] (dt. Aware of the problem )
• Prepositional phrases: [in P [France N " ]]

In the first variant of transformation grammar, the lexical categories noun (N), verb (V), adjective (A) and preposition (P) are mentioned as candidates for heads of a phrase. Further developments of transformational grammar in the 1980s and 1990s also allow functional categories as head modal verbs and flexion (Engl. Inflection , I), complementizers like that and determinative (Engl. Determiner , D).

Inflection Phrases (IP or I "), Complementizer Phrases (CP) and Determiner Phrases (DP or D") then look like this:

• [Poirot will I [abandon V [the investigation D " ] [after lunch P" ]] V " ]
• [that C [ I " Poirot will abandon the investigation after lunch]]
• [the D [detective N [with the funny accent P " ]] N" ]

This reinterprets the structures of the noun phrase and the verb phrase: The inflection on the verb or a modal verb in the verb phrase is now the head of the IP. The determinative (D) of the DP is no longer a specifier of the noun phrase, but the head of the DP.

## History and further developments

The X-bar theory was first formulated by Noam Chomsky as part of his transformation grammar in the 1970s, but its basic idea goes back to the structuralists who analyzed parts of sentences or phrases in hierarchical structures even before Chomsky. The X-bar theory is also an essential component in the further developments of transformational grammar, such as Chomsky's theory of rule and attachment . In later theory variants (for example the minimalist program ) more flexible and more economical models were discussed, which get by with less rigid specifications. The applicability of the scheme to OV languages is sometimes seen as problematic. The terminology of the X-bar theory, however, still belongs to the classic inventory of syntax theory.

## Applications

The X-bar theory is primarily part of theoretical work on syntax in the context of generative grammar. In the 1990s in particular, however, there were some approaches that also used the X-bar theory in applied linguistics : As part of transformation grammar as well as rule and attachment theory, the X-bar theory formed the basis for further research on first language acquisition , neurolinguistics and computational linguistics . Linguists who worked within the framework of rule and attachment theory assumed that rules of the X-bar syntax are innate in the child and enable him to learn language in all its complexity. Publications on first language acquisition used the X-bar theory to explain the acquisition of sentence structure and phrase structures in children. Some literature on neurolinguistics used the X-bar theory or the rule and attachment theory to describe agrammatism in aphasia patients.

## literature

• Noam Chomsky: Remarks on Nominalization. In: R. Jacobs and P. Rosenbaum (eds.): Readings in English Transformational Grammar. Ginn, Waltham MA 1970, pp. 184-221.
• Noam Chomsky: Lectures on Government and Binding. Foris, Dordrecht 1981, ISBN 3-11-014131-0 .
• Noam Chomsky: The Minimalist Program. MIT Press, Cambridge, Mass. 1995, ISBN 0-262-53128-3 .
• Gisbert Fanselow, Sascha W. Felix: Language theory. An introduction to generative grammar . Volume 2: The theory of rule and attachment , 3rd edition. Francke, Tübingen and Basel 1993, ISBN 3-8252-1442-7 .
• Naoki Fukui: Phrase Structure . In: Mark Baltin, Chris Collins (eds.): The Handbook of Contemporary Syntactic Theory. Blackwell, Oxford 2001. (= Blackwell handbooks in linguistics), pp. 374-406.
• Liliane Haegeman: Introduction to Government and Binding Theory , 2nd edition. Blackwell, London 1994, ISBN 0-631-19067-8 .
• Ray Jackendoff : -Syntax: A Study of Phrase Structure. MIT Press, Cambridge (MA) 1977.${\ displaystyle {\ bar {X}}}$
• Andrew Radford: Transformational Grammar: A First Course . Cambridge University Press, Cambridge 1988, ISBN 0-521-34750-5 .

## Individual evidence

1. ^ Andrew Radford: Transformational Grammar: A First Course . Cambridge University Press, Cambridge 1988, ISBN 0-521-34750-5 , p. 173.
2. Gisbert Fanselow, Sascha W. Felix: Sprachtheorie. An introduction to generative grammar . Volume 2: The theory of rule and attachment , 3rd edition. Francke, Tübingen and Basel 1993, ISBN 3-8252-1442-7 , p. 51.
3. ^ Andrew Radford: Transformational Grammar: A First Course . Cambridge University Press, Cambridge 1988, ISBN 0-521-34750-5 , p. 274.
4. ^ Liliane Haegeman: Introduction to Government and Binding Theory , 2nd edition. Blackwell, London 1994, ISBN 0-631-19067-8 , p. 84.
5. ^ Noam Chomsky: Lectures on Government and Binding. Foris, Dordrecht 1981, ISBN 3-11-014131-0 .
6. Steven Abney: The English Noun Phrase in Its Sentential Aspect . Dissertation, MIT, 1987.
7. ^ Liliane Haegeman: Introduction to Government and Binding Theory , 2nd edition. Blackwell, London 1994, ISBN 0-631-19067-8 , pp. 114, 117.
8. ^ Noam Chomsky: Remarks on Nominalization. In: R. Jacobs and P. Rosenbaum (eds.): Readings in English Transformational Grammar. Ginn, Waltham MA 1970, pp. 184-221.
9. ^ Noam Chomsky: Lectures on Government and Binding. Foris, Dordrecht 1981, ISBN 3-11-014131-0 .
10. ^ Noam Chomsky: The Minimalist Program. MIT Press, Cambridge, Mass. 1995, ISBN 0-262-53128-3 .
11. Gisbert Fanselow, Sascha W. Felix: Sprachtheorie. An introduction to generative grammar . Volume 2: The theory of rule and attachment , 3rd edition. Francke, Tübingen and Basel 1993, ISBN 3-8252-1442-7 , p. 20.
12. ^ Andrew Radford: Syntactic Theory and the Acquisition of Syntax . Blackwell, Oxford 1990.
13. Harald Clahsen (Ed.): Generative Perspektives on Language Acquisition. Empirical Findings, Theoretical Considerations and Crosslinguistic Comparisons . Benjamin, Amsterdam / Philadelphia 1996.
14. Helen Leuninger: Neurolinguistics: Problems, Paradigms, Perspectives . Springer, Wiesbaden 1989, ISBN 978-3-531-11866-6 .