This morning I was editing a proposal for my company when Microsoft Word threw a green squiggly under my word “which.” The program was recommending I either add a comma or change the word to “that.”
As one of my goals this year was to develop better comma habits, I decided to investigate further. In doing so I found this great website: Grammar Girl.
In one particular article Grammar Girl describes the differences between “which” and “that.” While I’m sure many of you are all over this, I didn’t remember the rule. Not even a little bit. In the spirit of knowledge sharing here are the details:
That should be used with restrictive clauses. This means if your clause is essential for the understanding of the sentence use that.
Which should be used with non-restrictive clauses. This means if your clause is just a fun ornament attached to your sentence to add flavor throw in some commas around the clause and use which.
Turkey that is covered in gravy may require more reheating in the microwave.
See how the gravy is critical for the sentence? Use that.
Turkey, which tastes great with gravy, is an essential part of Thanksgiving meals.
Suddenly the gravy is no longer critical so we’ve switched to which and added some commas.
UPDATE: Check the comments for a link to a better discussion on that vs. which courtesy of Whitney.