That vs. Which

A while back, someone (possibly here on SD) gave me a very simple way to remember the difference between its and it’s. Prior to hearing this new idea, the only rule I had ever heard was that its is only a possessive so it doesn’t get an apostrophe, but it’s is a contraction and contractions always get an apostrophe. But I got confused, because plenty of possessives get apostrophes, such as Jack’s car or the car’s roof.

So the new rule I heard was to focus on its being a possessive pronoun: His and hers don’t have apostrophes, and so neither does its. Since the day I heard that, I’ve never again been confused.

So here’s my question for this thread: Is there any similarly simple rule to know when to use that or which? In the vast majority of cases, both sound fine to my ear, but I know that’s wrong, and I’d like to improve. Any suggestions?


“That” is either a pronoun or an adjective used to identify a specific person, place, or thing.

“Which” is an old woman with green skin who flies around on a broomstick and makes potions.

(Apologies to Humphrey Lyttelton)

“Which one is it?” <— implying one of many

“That one!” <— specifying a particular one

I dunno if there’s a short and snappy rule. Traditionally, that starts off a restrictive clause while which starts off unrestrictive clauses. So, “I ate the candy that I had bought yesterday” and
“I ate the candy, which I had bought yesterday.” The former tells you of all the candy I may own, I ate only those pieces bought on the previous day. The latter just says that I ate some candy and oh by the way, I bought it yesterday.

It’s a nitpicky thing and personally I wouldn’t care about it in anything but an extremely formal paper and never in conversation.

“That” is used to identify one of several options. “Of all the chairs in this showroom, the one that is blue will match my sitting room.”

“Which” is used in the description of an item, where there is no question whicih item is being referred to. “The chair, which is blue, matched perfectly with my existing decor.”

Which follows a comma, that doesn’t. So the which part is a sub-part to the main story, whereas the that part is definitely a part of the main story line.

The dog that I chose from the pound was a Labrador.

  • the fact that the dog came from the pound is important.

The dog, which I chose from the pound, was a Labrador.

  • the fact that the dog came from the pound is an interesting aside, but I really want you to focus more on the breed.

Ironic sentence of the year award! :smiley:

The rule distinguishing between “that” and “which” isn’t a “real” rule of English anyway, as many speakers use the words almost interchangeably. It’s one of those rules invented by pedants in an effort to treat human language like a computer language, and good writers routinely ignore it:

Yet the distinction is very useful. Note that in this exception, an indefinite article is used, and the distinction between “that” and “which” is irrelevant: using it as restrictive or unrestrictive doesn’t change the meaning. After a definite article, the meaning would be different for restrictive versus unrestrictive.

People who ignore the distinction are tossing away a useful tool in the toolbox, and writing text that is more ambiguous than it needs to be.

As with any rule, there are plenty of exceptions. The way to tell whether the rule applies is to read it both ways, one where the prounoun should be restrictive (defining which item or items are referred to) or unrestrictive (merely adding description to the item – usually in a clause set off by commas). If that changes the meaning, use the best word. If it doesn’t change the meaning, it doesn’t really matter, so just go with your gut instinct.

Sure–but it’s a distinction invented by pedants, not one which is used naturally by native English speakers. If you want a useful language, try Esperanto or C++. English has got plenty of rules (consider the sentence “The chair black are full by comfort”–it breaks all sorts of real rules), but the supposed rule governing when to use “that” or “which” is more of an aspiration of pedants than it is a real rule.

I disagree. Lots of people use the terms the preferred way quite naturally, as do most good writers. The reason I say this with confidence is that I read a lot, and I notice careless usage since it bugs me, and I find I rarely see it.

If someone breaks the rule, is it wrong? Technically, no, since you can find a dictionary entry that allows it. But is it good style? Nope.

Eventually, all words will be synonyms and we won’t have these arguments. :wink:

That’s interesting, and doesn’t quite reflect my own observations. While I almost never hear “that” used in a non-restrictive (explanatory) clause, I hear “which” used for “that” in restrictive clauses all the time (including occasionally in my own speech.)

And the reason I say with confidence that you’re wrong is that the good folk at Random House find that 75% of the uses of “which” in edited prose introduce restrictive clauses. Unless you’re getting ready to make a No True Scotsman argument, you ought to concede that the rule is not normally followed.

Thanks, all! I will read these ideas and try to follow them!

The simple rule is to remember it’s always means “it is” or “it was”*. If you can read the line and substitute in one of those, it’s is correct - if you can’t, it isn’t.

Same thing with your and you’re. If you can substitute “you are” in the line, then you’re is correct - if not, it isn’t.

And don’t forget the other common possessive: whose. Who’s means “who is” not “belong to who”**.

*There’s one very rare exception. When you’re saying the word it possesses something. An example would be something like *“Gomez was amused by Cousin It’s remark.” *

**Same thing with who’s. Who’s can be a correct possessive if you’re talking about something possessed by who. Like “Amy Pond is my favorite of Dr. Who’s companions.”