Omitting relative pronouns

“The film we watched was brilliant.” Nothing is missing: that is optional because it would be the object of watched.

The one useful test

In a defining relative clause, you can often leave out who, which or that when it is the object of the clause:

• The book (that) I bought is here.
• The person (who) we met was friendly.

After the optional word, there is already a subject: I bought; we met. That is a good sign that the relative word is the object.

You cannot normally omit it when it is the subject:

• The book that won the prize is here.
• Not The book won the prize is here if you mean the prize-winning book.

Here that performs the action won.

Find who does the action before removing a word

Compare two sentences about a message:

The second becomes The message you sent was helpful. You have not removed an important meaning; the relationship remains clear.

Ask a question about the relative clause itself: Who does the action? In the neighbour who called, who does it and must stay. In the neighbour who I called, I does it, so the object who can be omitted.

Expand the short version to understand it

The shoes I'm wearing are new can look confusing because two verbs appear close together: am wearing and are.

Divide it into parts:

The shoes [I'm wearing] are new.

I'm wearing describes which shoes. Are new is the main message about them. Restoring that makes the relationship visible: The shoes that I'm wearing are new. The brackets are a learning aid; you do not need to write them in ordinary prose.

Build the clause carefully

Start with two short sentences:

I lost the keys. You gave me the keys.

Replace the repeated object with a relative clause:

I lost the keys (that) you gave me.

The object position after gave me is now understood. Do not add another object pronoun: the keys that you gave me them.

A preposition can remain at the end in everyday English: The colleague (who) I spoke to was helpful.

Do not omit every relative word

Do not leave out whose in a possession clause: The student whose bag is red is over there. In a non-defining clause with commas, the relative word is normally required: My brother, who lives in York, is visiting.

Keep the empty object position empty

Start with You recommended a book. I read the book. The relative clause version is I read the book you recommended.

Inside you recommended, the recommended thing is already understood: the book. Do not add it: the book you recommended it repeats the object.

The same applies with people: The friend we invited couldn't come, not the friend we invited her couldn't come. Removing the relative pronoun does not create a need for another pronoun at the end.

Prepositions can stay at the end

The chair I sat on was uncomfortable means the chair that I sat on. The preposition on is still necessary because you sit on a chair.

The person I spoke to was helpful keeps to for the same reason. In a more formal form, The person to whom I spoke ..., the pronoun follows a fronted preposition and cannot simply be omitted: not the person to I spoke.

Do not omit whose: The colleague whose laptop broke is using mine needs the possession link. Do not omit the relative word in a non-defining clause with commas: My laptop, which I bought last year, works well.

For a practical check, compare The cake we made was delicious and The cake tasted delicious was homemade. The first already has we as the subject of made, so omission works. The second needs that: The cake that tasted delicious was homemade.

This gives you a reliable method: check that the clause is defining, identify the relative word's role, and remove it only when it is an object in a construction that allows omission. If you are uncertain, keeping who/which/that is often the clearer option.

Sources and further reading

• British Council LearnEnglish: Defining relative clauses
• Cambridge Dictionary: Defining and non-defining relative clauses