Let’s say we have two distinct deep structures. One expresses the idea that “Annie had an umbrella and she bumped into a man with it.” The other expresses the idea that “Annie bumped into a man and the man happened to be carrying an umbrella.” Now, these two different versions of events can actually be expressed in the same surface structure form: Annie bumped into a man with an umbrella. This sentence provides an example of structural ambiguity. It has two distinct underlying interpretations that have to be represented differently in deep structure.

The comedian Groucho Marx knew how to have fun with structural ambiguity. In the film Animal Crackers, he first says I once shot an elephant in my pajamas, then follows it with How he got into my pajamas I’ll never know. In the non-funny interpretation, part of the underlying structure of the first sentence could be something like: “I shot an elephant (while I was) in my pajamas.” In the other (ho, ho) interpretation, part of the underlying structure would be something like: “I shot an elephant (which was) in my pajamas.” There are two different underlying structures with the same surface structure.

Phrases can also be structurally ambiguous, as in expressions like small boys and girls. The underlying interpretation can be either “small boys and (small) girls” or “small boys and (all) girls.” Our syntactic analysis will have to be capable of showing the structural distinction between these underlying representations.