That vs which and how to use them correctly

Where and when to use that vs which is a little complicated, so if you’re not sure if you’re using them correctly, you’re not alone. I work with a lot of professional writers and many of them use ‘which’ incorrectly. I see it used incorrectly in the media every day, which doesn’t set a good example for the rest of us.

When to use ‘which’ and when to use ‘that’

That and which can’t be used interchangeably. Using one or the other changes the meaning of a sentence.

When to use ‘that’

Use ‘that’ when you introduce a restrictive clause, (also known as an ‘essential clause’) into your sentence.

A restrictive clause means that the clause is essential to the meaning of a sentence. It restricts its meaning by limiting the thing or things it refers to.

We could fall into a rabbit hole of explanations here that about clauses are not entirely necessary to understand the difference between that and which. Instead, let’s get into some examples.

Here’s an example of using ‘that’ in a sentence with a restrictive clause:

  • The car that ran over the one-armed zombie was out of petrol.

In this sentence, I’m talking about a specific car— the one that ran over the one-armed zombie. So I use the word ‘that’ here rather than ‘which’. By using ‘that’ I’m suggesting that there was more than one car. It’s a restrictive clause because it limits all cars to just one car—the car that ran over the one-armed zombie. I distinguish this car from all other cars by using the restrictive clause.

When to use ‘which’

The opposite of a restrictive clause is a non-restrictive clause.

Use ‘which’ to introduce a non-restrictive clause that adds extra information to a sentence but doesn’t change the meaning of the sentence.

Here’s the same sentence, but using ‘which’ instead of ‘that’.

  • The car, which ran over the one-armed zombie, was out of petrol.

In this sentence, I’ve chosen to make the part about the car being the one that ran over the one-armed zombie, extra information. It doesn’t change the meaning of the sentence — that the car was out of petrol. I can write the sentence without the non-restrictive clause and it doesn’t change the meaning of the sentence.

  • The car was out of petrol.

I’m not talking about a specific car. If I was talking about a specific car, I’d use ‘that’ like I did in the original example.

To introduce a non-restrictive clause, use a comma before ‘which’ and place another comma after the non-restrictive clause.

That vs Which and how to use them correctly

That vs which: examples of incorrect use

Every day I read the ABC news and find examples of journalists using ‘which’ instead of ‘that’. I searched for an example before writing this blog post and found one in the first article I opened. Then I gathered a few more.

Can you pick up the difference in meaning in each?

That vs which: example 1

A double whammy! This article uses ‘which’ incorrectly in both the heading and the image captions. It introduces a restrictive clause but incorrectly uses ‘which’ instead of ‘that’ because the text refers to a specific tree.

It’s a restrictive clause because out of all the trees in all the world, the article refers to one specific tree—the one that started the bushfire.

That Vs Which example

❌ How the ABC located the tree which started the Gospers Mountain bushfire and the Sydney ‘mega-blaze’

✔️ How the ABC located the tree that started the Gospers Mountain bushfire and the Sydney ‘mega-blaze’

❌ The tree which started the Gospers Mountain bushfire

✔️ The tree that started the Gospers Mountain bushfire

We need to use ‘that’ in these examples because it’s a restrictive clause—the article refers to a specific tree.

That vs which: example 2

That Vs Which - incorrect use

❌ ‘City of Perth report finds systemic failings in ‘dysfunctional council’ which led to suspension

✔️ ‘City of Perth report finds systemic failings in ‘dysfunctional council’, which led to suspension

By inserting a comma before the ‘which’, it turns it into a non-restrictive clause. The bit about it leading to a suspension is extra information.

Here’s the second incorrect use on the same screen:

❌ An explosive report into the embattled city of Perth has found “greed, incompetence and mismanagement” was able to flourish during a period of turmoil which led to the entire council…

✔️ An explosive report into the embattled city of Perth has found “greed, incompetence and mismanagement” was able to flourish during a period of turmoil that led to the entire council being sacked…

I used ‘that’ here instead of ‘which’ because it’s a restrictive clause, citing the reason why the entire council was sacked.

That vs which: example 3

So close! Here we have an almost-correct example of ‘which’ in a news headline.

❌ Death Valley just recorded 54.4 degrees Celsius which, if verified, could torch the record book

✔️ Death Valley just recorded 54.4 degrees Celsius, which, if verified, could torch the record book

Note that the commas should come before ‘which’. This would show that what follows is a non-restrictive clause—you could take it out and the overall meaning of the sentence wouldn’t alter. The temperature could be a new record.

That vs which: example 4

The same article, further down the page, uses ‘which’ incorrectly.

❌ Even the official temperature record website notes there may have been a sandstorm at the time which could have affected the reading.

✔️ Even the official temperature record website notes there may have been a sandstorm at the time that could have affected the reading.

I read the information ‘could have affected the reading’ as restrictive, so I suggested replacing ‘which’ with ‘that’ rather than adding a comma before ‘which’. The part about the sandstorm affecting the reading is important to the overall meaning of the sentence.

Let me know in the comments below if this post has confused things for you or made the use of ‘that’ and ‘which’ much clearer.

If you enjoyed this post, you might enjoy reading Plain English tips.

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