Chapter 3
Basic Concepts of Syntactic
Theory
1 X-bar Theory
1.1 Rewrite rules and some terminology
We will start by looking at some general principles that determine the basic structure
of phrases and sentences. The perspective we will present claims that these principles
are simple because there are a very small number of them that apply to all structures.
In fact this theory claims there to be at most three different rules which determine the
nature of all structures in a language. These can be stated as follows:
(1) a X' Æ X YP
b XP Æ YP X'
c Xn Æ Xn, Y/YP
Recall from chapter 2, rewrite rules which tell us how structures of various kinds
decompose into their constituent parts. The rules in (1) are like these, only far more
general. The generality is achieved through the use of category variables, X and Y,
which stand for any possible category (nouns, verbs, prepositions, determiners, etc.).
Thus these rules tell us how phrases in general are structured, not how particular VPs,
PPs or DPs are.
The third rule in (1) introduces a position into the phrase called the adjunct. Given
that we have yet to introduce these elements we will put off discussion of this rule
until section 1.3. where we will give a fuller account of both adjuncts and the
adjunction rule.
The first rule (1a) is called the complement rule, as it introduces the structural
position for the complement (the YP of this rule). The structure it defines is given
below:
(2) X'
X YP
There are several things to note about this structure. First there are two immediate
constituents of the X' (pronounced “X bar”): X, which is called the head of the phrase
and the complement YP. The complement, which, as its label suggests is a phrase of
any possible category, follows the head. This is a fact about English and in other
languages the complement may precede the head.