I consider myself a pretty good writer. So it came as something of a shock when a professional editor informed me a few years back that I was using the words “which” and “that” incorrectly. I argued about it, it seemed kind of arbitrary, but when he explained it, it finally made sense. So if you care about decent writing, and would like to learn a simple trick to improve yours – then follow me below the fold.
So when should we use “which” and when “that?”
Consider the following 2 sentences:
1. The red balloon that Bill’s mother had given him burst when it hit the tree.
2. The red balloon, which Bill’s mother had given him, burst when it hit the tree.
These sentences illustrate the proper use of the words “that” and “which.” The meanings of the 2 sentences are clearly different. In sentence 1, Bill has more than one red balloon, so the phrase “that Bill’s mother had given him” identifies which of his many red balloons reached its sad demise. In sentence 2, Bill has only one red balloon, which makes its sentimental value as a gift from his mother all the more poignant.
Any sentence with a phrase starting with “which” must make sense when the phrase is removed. In sentence 2, this is the case, but in sentence 1, removing the phrase leaves the reader confused about which balloon actually broke. A phrase starting with the word “which” is descriptive and adds additional information, so the phrase is not essential in the sentence, but “that” is for identification, so the phrase is essential for unambiguous understanding.
These sentences illustrate an important property of the words “that” and “which”, namely “which” must always be preceded by a comma. The usage difference requires it. The implied pause when you hit the comma emphasizes the optional and parenthetical nature of the "which" clause. And of course, since commas delimiting phrases almost always come in pairs, the phrase in sentence 2 ending with “him” must end with a comma as well.
As a rule of thumb, if “that” sounds right, it probably is.
Here are 2 common mistakes:
3. The red balloon which Bill’s mother had given him burst when it hit the tree.
4. The red balloon that Bill’s mother had given him, burst when it hit the tree.
In sentence 3, the writer clearly intended “that,” or did he? The reader has to think about what the writer really intended to say. Does Bill have more than 1 red balloon or not?
In sentence 4, a comma has been inserted between the subject and predicate of the sentence, an obvious but fairly common mistake. Here is a case where the second comma is missing. Although the meaning of the sentence is still clear (sort of), the reader has to stop and go back to ask why there is a comma there.
Now try these:
5. The health care bill, which Hillary had helped write, died in committee.
6. The health care bill that Hillary had helped write died in committee.
They are both correct, but do you see the difference?? Take the phrase out – does it say what you intended to say?
So, fellow Kossacks, if you find me criticizing your usage, please don't be offended - it almost always means I think you are one small step away from a perfect composition.