Who, which, that — which to use? — englishillustrated.com

Understanding Relative Pronouns

Relative pronouns introduce relative clauses, which give extra information about a noun. The three most common relative pronouns are who, which, and that. Each one has a specific use depending on what noun you are talking about. Learning to use them correctly will make your writing clearer and more natural.

Who vs. Which vs. That

Use who for people. Use which for things, animals, or ideas. Use that for both people and things, but it is more common with things. In everyday English, that is very popular and often replaces who or which. However, which is preferred after commas when you add extra (non-essential) information about a noun.

Defining vs. Non-Defining Clauses

A defining relative clause gives essential information. You do not use commas. You can use that in these clauses. A non-defining relative clause gives extra information and uses commas. You cannot use that with non-defining clauses. Use who for people and which for things. For example: The woman who lives next door is a doctor (defining). My sister, who lives in Paris, is a doctor (non-defining).

How to Choose: Who, Which, or That?

Choosing between who, which, and that depends on what you are referring to and what type of information you are adding to your sentence. Here is a practical guide:

Pronoun	Use For	Example
Who	People only. Use in both essential and non-essential clauses.	The teacher who assigned the project is strict. / Ms. Chen, who assigned the project, is strict.
Which	Things, animals, or groups. Use mainly in non-essential clauses (set off by commas).	The book, which arrived yesterday, is excellent. / The committee, which meets monthly, approves the budget.
That	Things, animals, people (informal), or groups. Use in essential clauses (no commas) to define or identify.	The book that arrived yesterday is excellent. / The policy that we discussed is effective.

The scientist who discovered this element won the Nobel Prize.

Use "who" for a person in an essential clause defining which scientist.

Dr. Smith, who discovered this element, won the Nobel Prize.

Use "who" even in a non-essential clause when referring to a specific named person.

The telescope, which uses advanced technology, cost millions.

Use "which" for a thing in a non-essential clause set off by commas.

The telescope that uses advanced technology is in the observatory.

Use "that" for a thing in an essential clause to identify which telescope.

Quick tip: If you can remove the clause without changing the core meaning of the sentence, use which with commas. If the clause is essential to identify what you are talking about, use that without commas.

Formula

✔ Positive

noun (person) + who + verb + object

The girl who won the competition is my sister.

Examples

The man who helped me yesterday was very kind.

Defining clause · Person · No comma

My car, which is very old, still runs well.

Non-defining clause · Thing · With commas

The book that I read last week was amazing.

Defining clause · Thing · Common in everyday English

The teacher that we like is Mr. Johnson.

Defining clause · Person · Less formal than who

The restaurant where we ate, which opened last year, has excellent food.

Non-defining clause · Extra information · Formal

All the students who passed the exam will receive a certificate.

Defining clause · People · Essential information

When to use it

Describing People

Use who when you want to add information about a person. This is very common in daily conversation and writing.

"The teacher who gives us homework is very strict."

Describing Things

Use which or that when you want to describe objects, animals, or abstract ideas.

"The pizza that we ordered was delicious."

Adding Extra Information

Use which with commas when you add extra details that are not essential to understanding the sentence.

"My mother, who is a doctor, works long hours."

Identifying Which One

Use defining clauses with who or that to clarify which specific person or thing you mean.

"I want to talk to the student who scored the highest mark."

Signal words

who (for people) which (for things, animals, ideas) that (for both, more casual) comma before which (non-defining clause) no comma with that (defining clause)

Common Mistakes

Wrong

The woman which helped me was very nice.

✓

Correct

The woman who helped me was very nice.

Use who for people, not which. Which is only for things.

Wrong

The book, that I enjoyed, was a bestseller.

✓

Correct

The book, which I enjoyed, was a bestseller.

Use which (not that) in non-defining clauses with commas.

Wrong

The people who we met at the party was friendly.

✓

Correct

The people who we met at the party were friendly.

Use were (plural) because people is plural, not was.

Wrong

The car that needs repair, it is in the garage.

✓

Correct

The car that needs repair is in the garage.

Do not repeat the subject with a pronoun after the relative clause.

KEY TAKEAWAYS

What to Remember

Use who when referring to people in relative clauses.
Use which for things, animals, or ideas in relative clauses.
Use that for both people and things, though it's more common with things.
That is very popular in everyday English and often replaces who or which.
Relative pronouns introduce clauses that provide extra information about a noun.

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What are relative clauses?

Defining relative clauses