That v. Which

This one trips up a lot of people. If the information is essential, you should use ‘that.’ If the additional information is useful but not completely necessary, you would use ‘which.’

Can you tell the difference between these two sentences?

What’s the difference? In the first example, there are are plenty of red houses, but mine happens to have a blue chimney. That’s how you can tell it’s mine. In the second, my house is the only red house, and it happens to have a blue chimney.

In the first example, the blue chimney is key information, so it takes ‘that.’ In the second, it’s not, so you use ‘which.’ If you want to know the technical terms, the first is a restrictive clause while the second is nonrestrictive.

Let’s try some more.

In the first example, it’s a restrictive clause. There may have been many pies, but I’m talking about the one that I bought yesterday. In the second, which has a nonrestrictive clause, the fact I bought it yesterday isn’t all that important.

How about these?

In the first example there are many electric cars, but I’m referring to one that runs on a lithium-ion battery. In the second, the information contained in the clause is not completely necessary—many electric cars run on this type of battery.

One way to check this is to simply remove the information in the clause and see if the sentence makes sense. If it doesn’t make sense, it’s a restrictive clause and takes ‘that.’ If it does, it’s nonrestrictive and takes ‘which.’

Remove ‘that has no handle’ and what are you left with? A suitcase is useless. That doesn’t make sense, right? So it obviously needs ‘that.’

Same deal. A car won’t go far doesn’t make sense. So it’s got to be a restrictive clause, hence ‘that’: A car that has no gas won’t go far.

OK, try this:

In the first I only avoid cats I think that are dangerous. In the second I am saying that I think all cats are dangerous.

Last one:

In the first, a restrictive clause, a particular tweet upset her fans, so she deleted it. In the second, the fact that she removed the tweet was what upset her fans.

See how one word can completely changes the meaning of a sentence?

Exercise: Enter that or which in the space provided by clicking on this link.