Back to basics: Using which in a sentence

Do you struggle with when to use 'which'? Follow our grammar checklist to make sure you get it right

A lot of people (and a lot of writers) struggle with using ‘which’ in a sentence, believing it’s interchangeable with other words – who, that and what. But there are specific ways to use ‘which’ and we’ve put together a quick checklist to help you make sure you get it right,

Which vs who vs that as a pronoun

WHICH is used for things. WHO is used for people and THAT is used for either, though more usually in speech than in writing.

• The pan which I fry eggs in.

• The chef who fries eggs in the pan.

• The pan that the chef fries eggs in.

‘The detective which investigated the murder’ is wrong. The detective is a person. The detective who investigated the murder is right, and so is The detective that investigated the murder.

Which of these is right, and which is wrong?

• That’s the computer which broke down.

• She’s the runner which completed the marathon.

• I remember that woman which was on TV that did the comedy routine.

• The man who does the gardening is outside.

Which vs that after a comma

• The computer, which had broken, was being repaired.

WHICH should be used after a comma to introduce a non-restrictive clause. This means that if you take away the clause, the sentence still makes sense (The computer was being repaired). If the information being introduced with WHICH is additional information, it needs to be surrounded by commas if it’s in the middle of the sentence. The football boots, which were filthy, were left outside.

If the additional information is at the end of the sentence, it only needs one comma. She took off her football boots, which were filthy.

• The computer that had broken was being repaired.

All information in a non-restrictive clause is introduced by a comma. If you use THAT, no comma is used because THAT introduces information that is essential. The thieves stole the computer that had the database on it.

Which? vs what?

• What colour shall we paint the living room? Using WHAT suggests an unlimited selection of choices – the living room could be any colour.

• Which colour shall we paint the living room? WHICH suggests that the choice has been narrowed down to a selection of options.

WHAT? Is used when there’s an unknown or infinite number of possibilities? What day are we leaving? What book should I take?

WHICH? Suggests a choice between options. Which day are we leaving – Friday or Saturday? Which book should I take  - Jane Eyre or Crime and Punishment?

We hope this guide, which sets out some basic rules, helps. Now, what are you going write next? And which of your projects are you going to work on?

Want some more back to basics grammar advice? Check the 'A' and 'an' rule!