Phraseswould say that this formulation is more complex than it needs to be because
it fails to articulate a more general pattern. The broader generalization is that
these grammatical relations are always expressed as phrases and phrases can
consist of either a single word or a unified group of words. Below, we will
show how and when words can be phrases.
Second, single words and phrases may be replaced by identical proforms.
We can replace the subjects of both (1) and (2) with They:
(1) a. They fly.
(2) a. They fly.Again, there are two inferences we can draw: (a) pronouns can replace ei-
ther a noun or a noun phrase, or (b) pronouns replace phrases. Again, (b)
is more general, but it does require us to specify when words can function
as phrases.
A single word may be a phrase when it is the head of that phrase. The
head of a phrase is the phrase’s central element; any other words (or phrases)
in the phrase orient to it, either by modifying it or complementing it. The
head determines the phrase’s grammatical category: if the head is a noun,
the phrase is a noun phrase; if the head is a verb, the phrase is a verb phrase,
and so on. The head can also determine the internal grammar of the phrase:
if the head is a noun, then it may be modified by an article; if the head is
a transitive verb, it must be complemented by a direct object. Heads also
determine such things as the number of their phrases: if the head of an NP
is singular, then the NP is singular; if the head is plural, then the NP is
plural. Crucially, the head of a phrase may occur alone in the phrase, that is,
without modification or complementation.
Let’s look a little closer at what expressions may be replaced by pronouns.
Specifically, let’s test the claim made in many textbooks that pronouns can
replace nouns or noun phrases. Consider (3):
(3) Fooster hates the cabbage. NP
Det N
the cabbage
If we replace the NP the cabbage in (3) with the pronoun it we get the per-
fectly grammatical (3a):