The following is a brief compilation of some common problems with word choice and usage that have occurred in engineering theses and dissertations.
The dog that is on the bed needs a bath.
The dog, which is on the bed, needs a bath.
In the first sentence, there could be more than one dog, and the phrase on the bed defines which dog is meant. In the second sentence, there is only one dog; the phrase on the bed merely adds some descriptive information. Now note the following example:
The dog which is on the bed needs a bath.
In this sentence, the meaning is ambiguous. Proper use of which versus that and correctly adding commas would clarify the meaning.
Last modified April 10, 1998