79) S--NP VP
We thus have the rule that English sentences are composed of an NP and a VP, the precise
structural counterpart of the traditional ideas of a sentence being ‘a subject and predicate’ or ‘a noun and a verb’.
One more aspect to the structure of VP involves the presence of auxiliary verbs. Think of continuations for the fragments in (80):
(80) a. The students .
b. The students want .
For example, the phrases in (81a) and (81b) can occur in (80a) whereas those in (81c) can appear in (80b).