X-bar theory

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Syntax is the study of the principles and rules for constructing sentences in natural languages.

Contents

X-bar theory

The syntactic framework of the UNLarium derives from the X-bar theory [1], which postulates that all human languages share certain structural similarities, including the same underlying syntactic structure, whose abstract configuration is depicted in the diagram below:

    XP
   / \
spec  XB
     / \
    XB  adjt
   / \
  X   comp
  |
head

In the above:

  • X is the head, the nucleus or the source of the whole syntactic structure, which is actually derived (or projected) out of it.
  • comp (i.e., complement) is an internal argument, i.e., a word, phrase or clause which is necessary to the head to complete its meaning (e.g., objects of transitive verbs)
  • adjt (i.e., adjunct) is a word, phrase or clause which modifies the head but which is not syntactically required by it (adjuncts are expected to be extranuclear, i.e., removing an adjunct would leave a grammatically well-formed sentence)
  • spec (i.e., specifier) is an external argument, i.e., a word, phrase or clause which qualifies (determines) the head
  • XB (X-bar) is the general name for any of the intermediate projections derived from X
  • XP (X-bar-bar, X-double-bar, X-phrase) is the maximal projection of X.

Constituents

The head, the complement, the specifier and the adjunct are said to be the constituents of the syntactic representation and define the four general universal syntactic roles.

Heads

In the X-bar diagram depicted above, the letter X is used to signify an arbitrary category. Thus, the X may become an N for noun, a V for verb, and so on. In the UNLarium framework, there are eight different types of heads:

  • N = nouns and nominals: personal pronouns, demonstrative pronouns, nominalizations, etc
  • V = verbs
  • J = adjectives
  • A = adverbs[2]
  • P = prepositions
  • D = determiners: articles, demonstrative determiners, possessive determiners, quantifiers
  • I = auxiliary verbs
  • C = conjunctions

The heads define the nature of the phrase structures, thus:

  • N projects a Noun Phrase (NP)
  • V projects a Verbal Phrase (VP)
  • J projects an Adjective Phrase (JP)
  • A projects an Adverbial Phrase (AP)
  • P projects a Prepositional Phrase (PP)
  • D projects a Determiner Phrase (DP)
  • I projects an Inflectional Phrase (IP)
  • C projects a Complementizer Phrase (CP)
Noun Phrase Verbal Phrase Adjective Phrase Adverbial Phrase Prepositional Phrase Determiner Phrase Inflectional Phrase Complementizer Phrase
    NP
   / \
spec  NB
     / \
    NB  adjunct
   / \
  N   comp
  |
noun
    VP
   / \
spec  VB
     / \
    VB  adjunct
   / \
  V   comp
  |
verb
    JP
   / \
spec  JB
     / \
    JB  adjunct
   / \
  J   comp
  |
adjective
    AP
   / \
spec  AB
     / \
    AB  adjunct
   / \
  A   comp
  |
adverb
    PP
   / \
spec  PB
     / \
    PB  adjunct
   / \
  P   comp
  |
preposition
    DP
   / \
spec  DB
     / \
    DB  adjunct
   / \
  D   comp
  |
determiner
    IP
   / \
spec  IB
     / \
    IB  adjunct
   / \
  I   comp
  |
auxiliary verb
    CP
   / \
spec  CB
     / \
    CB  adjunct
   / \
  C   comp
  |
conjunction

Specifiers

Specifiers are used to narrow the meaning intended by the head. They include:

  • articles: the (book), a (book), etc.
  • possessive determiners: my (book), your (book), etc.
  • demonstrative determiners: this (book), that (book), etc.
  • quantifiers: no (answer), every (hour), etc.
  • intensifiers (emphasizers, amplifiers, downtoners): very (expensive), quite (well), nearly (under), kind of (like), etc.
  • frequency adverbs: always (go), never (go), usually (go), etc.
  • negative adverbs: not (go)

Complements

Complements are used to complete the meaning intended by the head. They may be:

  • direct objects: (do) something, (give) something
  • indirect objects: (laugh at) something, (give to) someone
  • complement of deverbals (i.e., nouns deriving from verbs): (construction of) the city, (arrival of) Peter
  • complement of adjectives: (loyal) to the queen, (interested) in Chemistry
  • complement of adverbs: (contrarily) to popular belief, (independently) from her
  • complement of prepositions: (under) the table, (after) today
  • complement of conjunctions: (and) Peter, (I don't know if) he'll come

Adjuncts

Adjuncts are used to modify the meaning intended by the head:

  • adjectives: beautiful (table)
  • manner adverbs: (speak) slowly
  • prepositional phrases: (table) of wood

etc.

Examples

NP VP JP PP
         NP
      /     \
     /       \ 
    /         \
   /          NB
  /         /     \
spec   head         comp
|        |           |
D        N           PP
|        |           |
the construction of Babel
                 VP
                 |     
                 VB
               /     \
              /       \
             /         \
            VB          \ 
          /    \         \
      head     comp      adjt
       |        |         |
       V        N         A
       |        |         |
(he) bought something yesterday
               JP
            /      \
           /        \ 
          /          \
         /            JB
        /          /     \
      spec     head       comp
        |        |           |
        A        J           PP
        |        |           |
(I'm) really interested in Chemistry
  
       PP
       |         
       PB         
     /    \
 head       N
  |         |
without   notice

Phrases

Specifiers, complements and adjuncts are themselves complex syntactic structures (XPs) which are combined to form the sentence structure:

PHRASE STRUCTURE
XP
SPEC XB
XB ADJT
HEAD COMP
NP DP N PP JP,PP
VP NP V NP,PP PP,JP,AP
JP AP J PP AP,PP
AP AP A PP PP,AP
PP AP P NP,JP,VP AP
DP AP D AP
IP AP I VP AP
CP AP C IP AP

Examples

construction the construction the fateful construction the fateful construction of Babel
     NP
     |
     NB
     |
     N
     |
construction
     NP
   /    \  
spec     NB
 |        |
 DP       N
 |        |
 DB  construction
 |
 D
 |
the
       NP
    /     \  
spec        NB
 |        /     \
 DP    adjt      N
 |      |        |
 DB     JP  construction
 |      |
 D      JB
 |      |
the     J
        |
       fateful
         NP
    /         \  
spec           NB
 |         /        \
 DP    adjt          NB
 |      |          /     \ 
 DB     JP       N       comp
 |      |        |         |
 D      JB  construction   PP
 |      |                  |
the     J                  PB
        |                /    \
       fateful         P      comp
                       |        |       
                      of        NP
                                |
                                NB
                                |
                                N
                                |
                               Babel

Properties

Branching is binary

A key assumption of X-bar theory is that branching is always binary, if it occurs. This means that specifiers, complements and adjuncts are optional and that there can be as many XBs as necessary:

  XP
  |
  XB
  |
 head
   XP
  /  \ 
spec XB
     |
    head
    XP
    |  
    XB
   /  \ 
head  comp 
    XP
    |  
    XB
   /  \ 
head  adjt 
   XP
  /  \  
spec  XB
     /  \ 
  head  adjt 
    XP
   / \
spec  XB
     / \
    XB  comp
   / \
  X   comp
  |
head
    XP
   / \
spec  XB
     / \
    XB adjt
   / \
  XB  comp
 / \
X   comp
|
head
etc.

Order is parametrized

The order of the constituents (specifiers, complements and adjuncts) is subject to language specific parametrization and may vary:

right complement left complement right adjunct left adjunct
    XP
    |  
    XB
   /  \ 
head  comp 
    XP
    |  
    XB
   /  \ 
comp  head 
    XP
    |  
    XB
   /  \ 
head  adjt 
    XP
    |  
    XB
   /  \ 
adjt head 
etc.

Conventions

The following conventions have been adopted in the UNLarium framework. They do not correspond to the current assumptions of the X-bar theory, and derive rather from extralinguistic issues (such as machine-tractability).

CP is the topmost level

In the UNLarium framework, a clause is considered to be an instance of the complementizer phrase (CP), which is the syntactic topmost level.

    CP
   /  \
spec  CB
     /  \ 
    C    IP 
        /  \
     spec   IB
            / \ 
           I   VP

C (i.e., the head of CP) is to be left empty in case of independent clauses (i.e., not introduced by any conjunction).

    CP
   /  \
      CB
     /  \ 
        IP 
        |
[Mary kissed Peter]
             CP
            /  \
                CB
              /    \
             /      \
            /        \ 
           C         IP 
           |          |
(I know) that [Mary kissed Peter]

IP represents finite clauses

The Inflectional Phrase (IP) is always the complement of the Complementizer Phrase (CP) and represents finite clauses. In the UNLarium approach, the head of IP is occupied only in case of compound tenses, i.e., by the auxiliary verb carrying information on tense, aspect and mood; in simple tenses, the head of the IP must be left empty.

    CP
   /  \
       CB
      /  \ 
          IP 
         /  \ 
             IB
            /  \ 
           I   VP
           |
       auxiliary
    CP
   /  \
       CB
     /   \ 
          IP 
         /  \
             IB
            /  \ 
           /    \
          /      \
         I       VP
         |        |
            [Mary kissed Peter]
    CP
   /  \
       CB
     /   \ 
          IP 
         /  \
             IB
            /  \ 
           /    \  
          /      \
         I       VP
         |        |
         is   [Mary kissing Peter]
    CP
   /  \
       CB
     /   \ 
          IP 
         /  \
             IB
            /  \ 
           /    \
          /      \
         I       VP
         |        |
       will   [Mary kiss Peter]
    CP
   /  \
       CB
     /   \ 
          IP 
         /  \
             IB
            /  \ 
           /    \
          /      \
         I       VP
         |        |
        may   [Mary kiss Peter]

etc.

Subjects

The subject of a clause is always represented at the position of spec of VP.

     VP
    /  \
Mary   VB
        |
     [died] 
     VP
    /  \
Mary   VB
        |
 [kissed Peter] 
     VP
    /  \
Mary   VB
        |
[gave a book to John] 
     VP
    /  \
Mary   VB
        |
  [is beautiful] 

etc.

Objects, Adjuncts and Predicates

There is no structural difference between objects (either direct or indirect) or adjuncts. They are always represented as branches of the intermediate projection. Predicates are represented as complements of copula (linking) verbs.

     VB
    /  \
  buy   NP 
        |
     [a car] 
     VB
    /  \
depend  PP
        |
     [on me] 
     VB
    /  \
  go   AP
        |
    [slowly] 
     VB
    /  \
  is   JP
        |
    [beautiful] 

etc.

Notes

  1. Chomsky, Noam (1970). Remarks on nominalization. In: R. Jacobs and P. Rosenbaum (eds.) Reading in English Transformational Grammar, 184-221. Waltham: Ginn.
  2. In the X-bar theory, differently from the UNLarium approach, adverbs are subsumed by prepositions and are not considered to be an independent lexical category.
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