Defining and non-defining relative clauses

Defining vs non-defining: Grammar chart

Defining relative clauses

Defining relative clauses carry essential information because they identify which thing or person we are talking about, and they are used without commas.

• This is the music which was used at the show. 
• Have they found the prisoner who escaped last week?

We can use that

In defining relative clauses, we can use that instead of which or who.

• This is the music that was used at the show. 
• Have they found the prisoner that escaped last week?

When can we omit who/which/that?

Who/which/that can be omitted if they are followed by subject + verb

• Can you pass me the box (which/that) I keep in the top drawer?
• You are not the man (who/that) I thought you were. 

Non-defining relative clauses

Non-defining relative clauses are used between commas, and they add extra information, which is not necessary to know who or what we are talking about.

• This music, which I really like, was used at the show.
• My sister, who I truly admire, is coming for Thanksgiving. 

We cannot use that, and we cannot omit who/which

In non-defining relative clauses (between commas), we cannot use that, and we cannot omit who/which.

• This music, that I really like, was used at the show.
• This music, which I really like, was used at the show.
• My sister, I truly admire, is coming for Thanksgiving. 
• My sister, whom I truly admire, is coming for Thanksgiving. 

Defining vs non-defining relative clauses

In a defining relative clause, the information is essential to identify who or what we are talking about, whereas in non-defining relative clauses, we just add extra information, which is not necessary. Compare:

• My brother who lives in Cardiff is much older than me. (=I have more than one brother, and the relative clause helps identify which brother I am talking about)
• My brother, who lives in Cardiff, is much older than me. (=I have only one brother, so we don’t need the relative clause to know who I am talking about)

Relative pronouns and adverbs

Here, you can see a grammar chart with the relative pronouns and adverbs that we normally use in relative clauses.

Common mistakes

Two subjects

When who, which, or that is the subject of a relative clause, we don’t use another pronoun or noun after it because we can only have one subject (who, which, or that). We can never have two subjects in a sentence.

• I saw a man who he was very tall. 
• I saw a man who was very tall. 
• That is the painting that it was stolen from the gallery. 
• That is the painting that was stolen from the gallery. 

That between commas

We cannot use the relative pronoun that in a non-defining relative clause (between commas)

• The victim, that suffered a concussion, said he didn’t remember the accident. 
• The victim, who suffered a concussion, said he didn’t remember the accident.