Difference Between: Which vs. That

Which or that?

Which

We use which to give non-essential information. This extra detail is placed inside commas or between a comma and a full stop. We can remove it without affecting the main meaning of the sentence. For example:

• My house is quite big. (basic fact)
• My house, which is on the other side of town, is quite big. (extra info)

If you can remove this extra information and the sentence still makes sense, then you are usually right to use which.

Examples of which in a sentence:

• I often visit my parents’ place, which is in London.
• My new shoes, which have red laces, are by the back door.
• The trains, which usually run on time, are late today.

That 

We use that to add essential information. This specifies a characteristic of the thing we are talking about, and makes it unique. We do not use commas before or after that. We cannot remove that without changing the main meaning of the sentence. For example:

• The clock that works is in the living room. (the working clock)

The fact that the clock works is essential to the meaning here. We are talking specifically about one particular working clock, and not the other broken clocks in the house.

Examples of that in a sentence:

• The film that I was telling you about is on again at the cinema.
• The train that is standing at platform 6 will be calling at Leeds, Derby…
• The book that I read last summer is still my favourite.

When both are possible

There are some situations when we can use both of these commonly confused words! Take the following two sentences for example:

• My computer that I use for work is expensive.
• My computer, which I use for work, is expensive.

These sentences look very similar, but they have different meanings.

In the first sentence, ‘My computer that I use for work’ is a specific computer that this person only uses for work. This information is essential because it shows how this computer is unique (compared to the other computers owned by this person). In other words, it is ‘my work computer’.

In the second sentence, ‘which I use for work’ is just one of many possible uses this computer could have. The focus of this sentence is the fact that the computer is expensive. We can also assume this is the person’s only computer.

Using commas with which and that

Commas can help us to understand where to use which or that. Remember, when we are speaking English, a short pause usually represents a comma in writing. 

1. There is often a comma before which and one after the extra information:

• The new house, which she liked immediately, was on George Street.

However, it is also common for this extra information to come at the end of a sentence. In this case, we only need a comma before which:

• The film starts at 9pm, which is great because I need to eat first.

The main meaning is: ‘The film starts at 9pm’. The person’s hunger is non-essential information and is added at the end.

2. We never use commas with that:

• Steve passed him a glass of water, that he drank immediately. (incorrect)
• Steve passed him a glass of water, which he drank immediately. (correct)

• The meeting, that had started ten minutes late, was about sales. (incorrect)
• The meeting, which had started ten minutes late, was about sales. (correct)

Exercises: Which or that?

Try these exercises to test your understanding of the differences between which and that. We have left out the commas to make this quiz more difficult. Think about where you would place commas in each sentence. Be careful because sometimes which or that are possible!

Sam S.
— ESL Tutor.

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