'That' vs 'Which': Definitions, Differences, and When to Use

You may have heard people use ‘that’ and ‘which’ interchangeably and wondered what the difference is between these words. If you’re still unsure, we’ll be covering that in this article, plus teaching you how to use both words in a sentence correctly. Plus, you’ll learn how to pronounce both words correctly.

Need a quick answer? Here it is:

• ‘That’ refers to something previously mentioned when introducing another clause, but ‘that’ introduces an essential clause.
• ‘Which’ also refers to something previously mentioned when introducing another clause, but ‘which’ introduces a non-essential clause.

A lot of people use the terms interchangeably, but the words are not synonymous, as you just saw. While they both refer to something previously mentioned when introducing another clause, there’s a difference. So, avoid swapping one word out for the other.

‘Which’ vs. ‘That’ – When to Use Each

It can be tricky trying to determine which word to use when it comes to ‘which’ and ‘that.’

But there’s a way to remember which to use.

Use ‘which’ when you’re discussing non-essential information.

Use ‘that’ when you’re discussing essential information.

Also, ‘that’ is used to describe an object, item, person, or condition, while ‘which’ is used to add information to objects, items, people, situations, etc.

‘Which’ usually comes right before a comma and at the end of the clause.

‘That’ vs. ‘Which’ – Difference and Comparison

The main difference between these words is that the former describes essential information, and the latter describes non-essential information.

The usage depends on whether the following clause is restrictive or non-restrictive.

The general rule, however, is that you use ‘that’ only to introduce a restrictive relative clause, which identifies the person or thing being talked about.

For example, you might say:

‘The red pants that I have are red.’

Or you might say:

‘That class that I dropped turned out to be more fun than I thought, according to my former classmates.’

Definition of ‘That’: What Does ‘That’ Mean?

The Merriam-Webster dictionary defines ‘that’ as:

• The person, thing, or idea indicated, mentioned, or understood from the situation.

It also means:

• The time, action, or event specified
• The kind of thing specified as follows
• One or a group of the indicated kind
• The one farther away or less immediately under observation or discussion
• The former one
• The one thing (something, anything)
• Some persons
• Being the person, thing, or idea specified, mentioned, or understood
• So great a (such)
• At which
• According to what
• That which
• The person who

Definition of ‘Which’: What Does ‘Which’ Mean?

The same dictionary defines ‘which’ as:

• Being what one or ones out of a group.

It also means:

• Whichever
• What one or ones out of a group
• Used as a function word to introduce a nonrestrictive relative clause

Pronunciation: How to Pronounce ‘That’ and ‘Which’ 

Are you curious about how to pronounce these words? Here’s a short guide.

To pronounce ‘that’ correctly, here’s the phonetic spelling:

thAt

To pronounce ‘which’ correctly, here’s the phonetic spelling:

wIch

How to Use ‘That’ and ‘Which’ in a Sentence

Now that we’ve got the definition and pronunciation out of the way, let’s see some examples of how to use both words in a sentence correctly.

That

• I didn’t know that there were more sodas. When did mom go to the store?
• We weren’t sure that we’d have enough sandwiches for everyone. We thought we might just have to order pizza.
• The partners said we’d have lunch and discuss my future at the company. I think I’m getting a promotion!
• My mom didn’t tell me that we had company. I came into the house singing at the top of my lungs, only to be embarrassed when I saw my auntie sitting there.
• It’s kind of stupid that we have to log in to view messages. They should just write the messages within the actual email to save us time and headaches.
• After a long time doing my own taxes, I realized that I was doing them wrong. I could have gotten back a lot more money if I’d let a tax professional do it.

Which 

• We have a lot of people coming today for the afternoon service, which means we need to make a few more plates for the after-service dinner.
• We have to be on time for our appointment, which is at 1:30. Are you going to make it here to get me in time?
• Which is it going to be? Her or me? You have to make a decision about who you want to be with, and you have to do it now.
• If we went to the store now, we wouldn’t make it home on time for the game, which I’m not willing to miss. Can you go alone?
• Which dress should I wear on my date with Stephen? I can’t decide whether I like the blue one more or the red one.
• We have a lot of work to do today, which I’m not too happy about. But what can we do? The work needs to be done, right?

Final Thoughts on ‘That’ and ‘Which’ 

To recap, we learned that:

• ‘That’ means something previously mentioned when introducing another clause, but ‘that’ introduces an essential clause.
• ‘Which’ also refers to something previously mentioned when introducing another clause, but ‘which’ introduces a non-essential clause.

Remember, many people use the terms interchangeably, but the words have different meanings, as you just saw. While they both refer to something previously mentioned when introducing another clause, there’s a difference. So, don't use them interchangeably in any case in your writing.

If you ever get stuck on the meaning or usage, feel free to come back here and review what you learned. We’ve got a ton of other content on confusing words and phrases you might see as you’re learning the language. Go check it out anytime.