X-bar theory

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

X-bar theory

The syntactic framework of the UNLarium derives from the X-bar theory , 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  adjunct
   / \
  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)
• 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.

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.

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.

Constituents

Heads

In the UNLarium approach to the X-bar theory, the heads, which should replace the letter X, may be occupied by the following categories

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

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

• N is the head of the Noun Phrase (NP)
• V is the head of the Verbal Phrase (VP)
• J is the head of the Adjectival Phrase (JP)
• A is the head of the Adverbial Phrase (AP)
• P is the head of the Prepositional Phrase (PP)
• D is the head of the Determiner Phrase (DP)
• I is the head of the Inflectional Phrase (IP)
• C is the head of the Complementizer Phrase (CP)

Specifiers

Specifiers are used to narrow the meaning intended by the head:

• 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:

• 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.

Phrases

Specifiers, complements and adjuncts are themselves complex syntactic structures (XPs):

PHRASE	STRUCTURE
	XP
	SPEC	XB
		ADJT	XB		ADJT
			HEAD	COMP
NP	DP	JP	N	PP	JP,PP
	the	fateful	construction	of Babel	by mankind
	many	beautiful	tables		of wood
	no		one

which are combined to form the sentence structure:

construction	the construction	the fateful construction	the fateful construction of Babel
NP | NB | N | <b>construction</b>	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