those who follow the MLA and the APA conventions, on the other hand, do
put the comma before the conjunction.
With regard to prepositional phrases, there are two conventions governing
punctuation of phrases in the initial position. One holds that writers should use
length as the basis for deciding whether to set the modifier off with a comma. In
this convention, short structures are not set off, whereas long ones are. Al-
though this approach is perfectly acceptable, it creates problems for teachers
whose students want as much consistency as possible.
Another convention holds that all modifying structures at the beginning of
sentences should be set off with a comma. Many teachers have adopted this
convention because it is easier to teach, or at least it is easier for students to ac-
cept. They do not have to think about length.Ambiguity
Language is inherently ambiguous, but certain prepositional phrase construc-
tions are quite obviously so. Under normal circumstances, we use context to
disambiguate such constructions, but it is possible to provide a grammatical
analysis that also disambiguates. Consider the following sentences:- Fred built the bench in the garage.
- Macarena put the shoes in the box in the closet.
All ambiguous sentences have two possible meanings.^1 In sentence 16, one
meaning could be that the act of building the bench could have taken place in
the garage. The second meaning could be that the act of building could have oc-
curred anywhere other than the garage, but the bench is in the garage now. In
sentence 17, the shoes already could be in the box, and Macarena put those par-
ticular boxed shoes in the closet. The other meaning could be that the empty
box already could be in the closet, and Macarena put the shoes in that box.
We can use grammatical analysis to disambiguate sentences like 16 and
17 because each possibility has a different phrase-structure, as illustrated in
the diagrams on pages 115 and 116.Coordination
Coordination is one of the more common features of language, and phrase-
structure grammar provides a rule that is generally applicable to all coordinated114 CHAPTER 4(^1) Although the possibility exists for more than two meanings, examples are so rare that none could be
found for this text.