Defining vs Non-Defining Relative Clauses

Essential vs extra information in English relative clauses

🟦Defining Relative Clauses

Defining relative clauses carry essential information because they identify which person or thing we are talking about. 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, that can replace who or which.

✅ 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?

You can omit the relative pronoun if it is the object of the clause (i.e., when it’s followed directly by a 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 add extra, non-essential information. They are always set off by commas.

✅ 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 clauses (between commas), that is not allowed, and the relative pronoun must be included.

❌ 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: Key Difference

In a defining clause, the information is essential to identify the noun. In a non-defining clause, it’s just extra detail.

✅ My brother who lives in Cardiff is much older than me.
(= I have more than one brother; the clause identifies which one.)
✅ My brother, who lives in Cardiff, is much older than me.
(= I have only one brother; the clause adds extra info.)

🟨Relative Pronouns and Adverbs

Common relative words used in English relative clauses:

Relative Word	Use	Example
who	People (subject)	The woman who called you is my boss.
whom	People (object – formal)	The man whom I saw was tall.
which	Things / animals	The book which you lent me is great.
that	People / things (defining only)	The car that broke down was old.
where	Places	This is the town where I was born.
when	Time	I remember the day when we met.
whose	Possession	The student whose essay won is here.

🟥Common Mistakes

1. Two Subjects

When who, which, or that is the subject of the relative clause, do not add another subject.

❌ 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.

2. Using that in Non-Defining Clauses

Never use that 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.

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