they exhibit. English verbs appear in a number of distinct forms, whereas
modals have a single, invariant form. For instance, modals never end in-s,even
in sentences with third-person singular subjects.
To include the modal in our grammar, we simply expand the rule for auxil-
iary to account for tense markers (past and present) and modals, as shown:
AuxÆtense (M)MÆwill
shall
can
may
mustìíï
ïïîï
ï
ïüýï
ïïþï
ï
ïWith this modification to our rules, we can describe sentences such as 24:- Fritz may get a promotion.
Analysis of this sentence is shown in the following tree diagram on the
next page.
A question that often arises in the analysis of expanded verb phrases is why
the tense marker is placed in front of the verb rather than after. The past parti-
ciple suffix -ed/-en, after all, comes at the end of a verb, not at the beginning.
The answer is that there is no simple way to capture schematically the rela-
tions among tense, modals, and verbs. Whenever a verb has a modal, the
modal is tensed, not the verb. If our description put tense after the verb, we
would solve nothing—we would still have the question of how tense jumps
over the verb and attaches to the modal. The placement of tense at the head of
the VP is a matter of convention; placing it elsewhere in the VP would not en-
hance the description.
What we learn here is that structural analyses are at best an approximate de-
scription of the language we actually use. If we wanted to account for the fact that
the past participle appears at the end of verbs, we would have to develop a special
126 CHAPTER 4