A down-and-dirty guide to that vs. which

Explaining the difference between “that” and “which” has been in my idea file for a while. Don’t feel bad if you don’t know the answer – it’s a common conundrum. Now that I’ve had requests to cover this topic, your wait is over!

I’m all about instant gratification, but first you must grasp essential and nonessential clauses, often referred to as restrictive and nonrestrictive clauses.

You cannot eliminate an essential clause from a sentence without changing the meaning of that sentence. In other words, an essential clause helps define the meaning of a sentence. “That” introduces an essential clause. Some examples follow:

I remember the day that we met in Paris.
This sentence wouldn’t make any sense if I wrote, “I remember the day which we met in Paris.”

That is a decision you must live with.
You’d definitely get some strange looks if you said, “Which is a decision you must live with.”

The senator said that he might run again and that, if he did, Mary Rosenthal would be his campaign manager.
Same principle as the previous examples.

You can delete a nonessential clause from a sentence without changing the basic meaning of that sentence. Think of a nonessential clause as a way to elaborate. “Which” introduces a nonessential clause:

The soccer team’s trophy, which was displayed in the main hallway, is missing.
If you delete the nonessential clause, “which was displayed in the main hallway,” the rest sentence stands on its own. You know that the trophy is missing and, thanks to the nonessential clause, you know where it’s missing from.

He downloaded numerous software updates to his computer, which is the most expensive model he could get.
Taking out, “which is the most expensive model he could get,” doesn’t change the meaning of the rest of the sentence. The nonessential clause just tells you that the guy had a lot of money and could afford a pricey computer.

The company’s new product line includes advanced sorters, which feature adjustable controls and multifunctional monitoring stations, will be unveiled next week.
The important information here is that the company will reveal a new product line next week. If you can’t wait to learn more, the nonessential clause, “which feature adjustable controls and multifunctional monitoring stations,” shares some of the juicy details.

Tip: Essential clauses, phrases or words do not need to be set off from the rest of a sentence, so they don’t need commas. In contrast, commas separate nonessential clauses.

Are you up to speed on “that” vs. “which” now? If you still have questions, check out this excellent Grammar Girl post from Mignon Fogarty.

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