What is a Non-Defining Relative Clause?
A non-defining relative clause gives extra, non-essential "bonus" information about a noun. The noun being described is almost always already specific and known to the listener (e.g., a proper name, a unique title, or a noun with a possessive pronoun like 'my').
If you remove a non-defining relative clause from the sentence, the core factual meaning remains perfectly clear and intact. Think of it as a "by the way" conversational comment inserted into the middle of a sentence.
- My brother, who currently lives in London, is a professional doctor.
Here, the main independent factual information is "My brother is a professional doctor." The fact that he lives in London is just extra detail. We logically already know which brother we're talking about without that clause.
Non-Defining Relative Clause Structure and Formula
The structure mirrors standard relative clauses but is heavily heavily dependent on commas to act as brackets or parentheses.
S + , + Relative Pronoun + V + O + , + V + O
The Absolute Golden Rule: You must always use commas to separate a non-defining clause from the rest of the sentence. The commas physically trap the non-essential information.
- The Eiffel Tower, which is in Paris, is famous worldwide.
- I'm going to visit my grandmother, who is 90 years old.
List of Relative Pronouns for Non-Defining Clauses
| Relative Pronoun | Grammatical Target | Example Sentence |
|---|---|---|
| who | People (Subject style) | My friend Sarah, who is a talented musician, is joining a rock band. |
| which | Things / Objects | My beautiful phone, which I only bought last year, is shockingly broken. |
| whose | Possession | The author, whose recent books are bestsellers, is giving an open talk tonight. |
| where | Places / Locations | London, where my older brother lives, is a vibrant bustling city. |
| whom | People (Formal Object style) | The CEO, whom many people deeply respected, suddenly announced his resignation. |
How to Comment on a Whole Sentence Using "Which"
A very unique, advanced feature of non-defining clauses is that the pronoun which can be used to refer to the entire idea of the preceding clause, not just a single physical noun!
He completely forgot my birthday, which genuinely made me sad.
(What made me sad? The overall situation that he forgot).We practically had to cancel the outdoor picnic, which was a real shame.
(What was a shame? The action of cancelling).
How to Tell the Difference Between Defining and Non-Defining Relative Clauses
The difference entirely revolves around whether the information identifies the noun or just describes it.
| Feature Check | Defining Clause (Essential) | Non-Defining Clause (Extra) |
|---|---|---|
| Purpose | Strictly identifies which noun we mean. | Strictly gives bonus description. |
| Comma Rule | Never use commas. | Always use commas. |
| Using "That" | Yes, you can comfortably use "that". | No, never ever use "that". |
| Omission | You can drop object pronouns. | No, never omit the pronoun. |
Frequently Asked Questions
Can I use "that" in a non-defining clause?
Absolutely not. This is a very common punctuation and grammar error. You can never use the word that immediately after a comma in a relative clause.
* Incorrect: My car, that is very old, often breaks down.
* Correct: My car, which is very old, often breaks down.
Can I omit "who" or "which" like I can in defining clauses?
No. Because the information is separated by commas, the clause must structurally stand fully intact on its own within those commas. You must definitively include the relative pronoun.
* Incorrect: My boss, I admire a lot, is retiring.
* Correct: My boss, whom I admire a lot, is retiring.
Does placing commas change the actual meaning of the sentence?
Yes! "The students who failed the test must stay after class." (Only the failing students stay). vs. "The students, who failed the test, must stay after class." (All the students failed, and all of them must stay).
Summary & Cheatsheet for Non-Defining Relative Clauses
| Rule to Follow | Grammatical Explanation | Example |
|---|---|---|
| Identify Extra Info | Use when the noun is already explicitly known. | My mother, who is a doctor, called me. |
| Use Commas | Trap the clause between commas like parentheses. | The car, which is red, is fast. |
| Ban "That" | Force yourself to use "who" or "which". | Mr. Smith, who is my teacher, is kind. |
💡 The key takeaway: If the noun is already highly specific, named, or unique, the following relative clause is non-defining. You must lock it between commas and you are strictly banned from using the word "that"!