How to Use Who, That, and Which: Easy-to-remember Explanation + Quiz

How to Use Who, That, and Which: Easy-to-remember Explanation + Quiz

  • Who and that are used for people.
  • That and which are used for things.
  • Which cannot be used for people.

To understand when to use them in a sentence we should understand relative clauses.

What are relative clauses

A relative clause is a sentence within a sentence which is related to the main sentence.

I like the woman who lives next door.

The main sentence: I like the woman
The relative clause: who lives next door 

Whether we use ‘who’, ‘that’, or ‘which’ depends on the type of a relative clause: defining or non-defining.

Defining Relative clauses Non-Defining Relative clauses 
  • give a sentence a meaning
  • if we cut them out the sentence will lose the meaning
  • no commas 
  • don’t give a sentence a meaning
  • add some extra information 
  • we can lose them without losing the meaning
  • We need to use commas
I like the woman who lives next door.  

If we take out ‘who lives next door’ from this sentence, it won’t make any sense: “I like the woman.”

He lives in London, which is the capital of the UK. 

If we take out ‘which is the capital of the UK’ the sentence will still make sense: “He lives in London.”  


How to use ‘which’, ‘who’ and ‘that’ in relative clauses
  • Which, that and who can be used in defining and non-defining relative clauses.
  • That cannot be used in non-defining clauses.

❌He lives in London, that is the capital of the UK.

When can we omit that/who/which

We can omit that/who/which if it’s in a defining clause and it’s not a subject.


Can omit Can’t omit
She likes the book that I bought her.  

That is not a subject, so we can omit it: She likes the book I bought her.  

I need a secretary who can type quickly.


Who – is a subject in the sentence “Who can type quickly”, so we can’t omit it. 

We can’t omit which  in a non-defining clause.

My boss, who is Nigerian, lives in Cape Town. 

Who is the subject in “who is Nigerian” and we can’t omit it. 

Last month  I bought a new dress, which I don’t like  now. 

Which is not a subject but we still can’t omit it.  

If it’s clear, take the quiz to strengthen your knowledge.

My Multiple Choice Quiz

How to Use Who, That, and Which: Easy-to-remember Explanation + Quiz

Practice more with these exercises.
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Want to learn more? Check out this section.

Who, Which, That: The Blue Book of Grammar
Perfect English: Relative Clauses
English Grammar in Use by Raymond Murphy

Which: Cambridge Dictionary

That vs Which: Purdue University

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