Understanding Relative Clauses Pt. 3 – Advanced Use Cases

👈 Just arriving? Start at the beginning: Part 1: Who, Which & That | Part 2: Defining vs. Non-Defining & Omitting Pronouns

⏭️ Already know the theory? Go straight to the full quiz!

You've mastered the core relative pronouns and the defining/non-defining distinction. Now let's go further — prepositions, "what," quantifiers, all the common mistakes, and a full set of practice exercises. Let's finish strong! 🚀

Prepositions in Relative Clauses

In formal English, prepositions can go before "which" or "whom." In informal English, they go at the end — which is how most people actually speak.

Formal (preposition before):

• The hotel in which we stayed was excellent.
• The woman to whom I spoke was very helpful.
• The issue about which we're concerned is serious.

Informal (preposition at the end):

• The hotel which we stayed in was excellent.
• The hotel we stayed in was excellent. ✅ (most natural)
• The woman I spoke to was helpful. ✅

Important: You cannot use "that" directly after a preposition:

• ❌ The hotel in that we stayed...
• ✅ The hotel in which we stayed... (formal)
• ✅ The hotel that we stayed in... (informal)

WHAT — A Special Case

"What" means "the thing(s) that" — and unlike other relative pronouns, it doesn't need a noun before it.

• What you need is a vacation. (= The thing that you need)
• I don't understand what he said. (= the thing that he said)
• What happened was surprising. (= The thing that happened)

Compare: What I bought was expensive. = The thing that I bought was expensive. (same meaning)

Quantifiers with Relative Clauses

We can use quantifiers (all, some, many, none, etc.) before "of which" or "of whom." This is a more advanced structure but very useful.

• I have three brothers, all of whom are doctors.
• She has ten books, some of which are very old.
• I invited twenty people, none of whom came.
• There were 50 students, many of whom passed the exam.

Pattern: noun + comma + quantifier + of which/whom + verb

Quick Reference: Advanced Structures

Structure	Use	Example
Preposition + which/whom	Formal writing	The hotel in which we stayed...
which/that + preposition at end	Informal / spoken	The hotel we stayed in...
what	"The thing(s) that" — no noun needed before it	What you need is rest.
quantifier + of which/whom	Referring to part of a group	...twenty guests, none of whom came.

Common Mistakes — The Full List

❌ Mistake 1: Forgetting commas in non-defining clauses

• ❌ My sister who lives in Paris is a doctor. (suggests I have more than one sister)
• ✅ My sister, who lives in Paris, is a doctor.

❌ Mistake 2: Using "that" in non-defining clauses

• ❌ My sister, that lives in Paris, is a doctor.
• ✅ My sister, who lives in Paris, is a doctor.

❌ Mistake 3: Using "what" instead of "that"

• ❌ The book what I read was good.
• ✅ The book that I read was good.

❌ Mistake 4: Omitting subject pronouns

• ❌ The man called you is waiting.
• ✅ The man who called you is waiting. (subject — must keep!)

❌ Mistake 5: Wrong relative pronoun

• ❌ The woman which I met was nice.
• ✅ The woman who I met was nice.

❌ Mistake 6: Double subject

• ❌ The man who he lives next door is friendly.
• ✅ The man who lives next door is friendly.

❌ Mistake 7: "That" after a preposition

• ❌ The hotel in that we stayed was excellent.
• ✅ The hotel in which we stayed was excellent. (formal)
• ✅ The hotel that we stayed in was excellent. (informal)

Practice Exercises

Time to put it all together! Work through these, then check your answers below. No peeking! 👀

Exercise 1: Formal or informal? Rewrite in the other style.

1. Formal: The hotel in which we stayed was excellent. → Informal: _______
2. Informal: The woman I spoke to was helpful. → Formal: _______

Exercise 2: Spot and correct all the mistakes.

3. The woman which I met was nice.
4. My sister, that lives in Paris, is a doctor.
5. The man called you is waiting.
6. The book what I read was good.
7. The hotel in that we stayed was excellent.
8. My sister who lives in Paris is a doctor. [I have one sister]

Exercise 3: Fill in the gap — what, quantifier + of which/whom.

9. I don't understand _______ he said.
10. She bought five dresses, _______ were on sale.
11. I invited thirty people, _______ came.
12. _______ you need is more practice.

Exercise 4: Define or non-define? Add commas where needed.

13. People who exercise regularly are healthier. [which people? — defining]
14. John who is my best friend got married last year. [we know who John is]

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Answers

Exercise 1

1. The hotel we stayed in was excellent. (or: The hotel that we stayed in was excellent.)
2. The woman to whom I spoke was helpful.

Exercise 2

3. The woman who I met was nice.
4. My sister, who lives in Paris, is a doctor.
5. The man who called you is waiting.
6. The book that I read was good.
7. The hotel in which we stayed was excellent. / The hotel that we stayed in...
8. My sister, who lives in Paris, is a doctor. (commas needed — one sister)

Exercise 3

9. what
10. some of which
11. none of whom
12. What

Exercise 4

13. People who exercise regularly are healthier. (no commas — defining)
14. John, who is my best friend, got married last year. (commas needed)

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How did you do? If you're feeling solid, the full interactive quiz below is the perfect final test. If a few answers surprised you, go back and re-read the relevant section in Part 2 before you try it — you'll do much better! 💪

🎯 Take the full interactive Relative Clauses quiz!

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👈 Part 1: Who, Which & That | Part 2: Defining vs. Non-Defining & Omitting Pronouns

Part of the LearnFast.life Grammar Series

Practice Quiz

Click here to take the interactive quiz