Ambiguity, there being more than one meaning, can be divided into semantic and syntactic ambiguity (there are different ways of classifying ambiguities, but we'll keep things simple here). An example of the first kind may be found in the sentence
Here the source of the ambiguity is the word 'bank', which could refer to both the building where one would go to for getting money and to what borders a river. So ambiguity can stem from the meaning of words. In syntactic ambiguity the ambiguity arises from the way the sentence is put together. The grammatical construction of the sentence or phrase leaves room for more than one way reading.
a.) As a demonstration of how ambiguous a language such as English may be, we give you sentence 2. How many different readings of this sentence can you find?
b.) Lets now focus on syntactic ambiguity only. Take a look at the following sentence:
In what ways is this sentence ambiguous? See if you can draw trees for each possible meaning with the treebuilder below. Use the following symbols for nonterminals:
c.) Eliminate half of the readings by only reshuffling phrases. Which phrase must be moved to the front of the sentence?
* Sentence taken from Wasow, T., Perfors, A., & Beaver, D. I. (2003). The puzzle of ambiguity. In P. Sells (Ed.), Essays in Honor of Steve Lapointe. Stanford, CA: CSLI Publications.