clauses nevertheless are deemed nonrestrictive. They have to be because as
adverbials they must modify either a VP or an S. In the initial position, they
can modify only an S.
With certain verbs, subordinate clauses can function as complements, as in:
- We wonderedwhether the fish were fresh.
- They could not decidewhether the trip was worth the cost.
In an ideal world, we would be able to write a phrase-structure rule that
describes all these structures and that also captures the fact that a subordi-
nate clause functions adverbially as part of the verb phrase or as a sen-
tence-level modifier. But there is no way to provide such information in the
rule, so we must be satisfied with a rule that just describes the structure; only
diagrams can illustrate how the SC functions. Several possibilities exist for
rules, but the simplest seems to be one similar to the XP rule we used for co-
ordination. If we think of a dependent clause as S(read bar-S), our rule
would be:
XPÆXP SSÆSconj NP VPThe first expression states that any phrase, XP, can be rewritten as that phrase
plus S.S, in turn, can be rewritten as a subordinating conjunction (Sconj), a noun
phrase, and a verb phrase. Stated another way, any XP may have a Sattached to it.
As in the rule for coordination, XP can represent either a clause or a phrase. We
must explain outside the rule, as a constraint, that Sattaches either to S or VP. We
can do this because the grammar is concerned primarily with describing existing
sentences. If structuralists had given the grammar a generative component—that
is, if it were more concerned with how people generate sentences with subordi-
nate clauses—they might have attempted to develop an expression that addresses
the question of placement. Without this concern, the issue is moot because place-
ment is given in the utterance being described.
We want a rule that is very generalizable, of course, so shortly in this chapter
we expand the definition of Sto include other types of dependent clauses,
which means that Sattaches to various types of phrases.
A couple of diagrams can make it easier to understand the nature of SC mod-
ification. Consider these diagrams for sentences 45 and 46:
PHRASE STRUCTURE GRAMMAR 137