Chapter 3 - Basic Concepts of Syntactic Theorywhich determine this. Recall that part of the lexical entry for a word concerns its
subcategorisation. The subcategorisation frame of a lexical element tells us what kind
of complement there can be. For fall, for instance, it is specified that the complement
is prepositional:
(23) fall category: [–F, –N +V]
-grid: <theme, path>
subcat: prepositional
Thus through the notion of subcategorisation, the head imposes restrictions on the
complement position, allowing only elements of a certain category to occupy this
position:
(24) VP
YP V'
V PP
fall
As we know that the complement must be prepositional, we also know by the
general principles of X-bar theory that only a preposition could be inserted into the
head position of this phrase and the lexical properties of this head will, in turn, impose
restrictions on what can appear in its complement position:
(25) VP
YP V'
V PP
fall P'
P DP
off the shelf
In this structure, off is inserted into the head position of the PP complement of the verb
and as this preposition selects for a DP complement (as most of them do), only a
determiner could be inserted into the head position of this phrase. The determiner
would then impose restrictions on its complement, ensuring this to be an NP and hence
only a noun could be inserted into the head of the determiner’s complement.
Obviously, this could continue indefinitely, but in this case the process stops at this
point as the noun subcategorises for no complement.