Non-defining relative clauses help us add extra information about a person, place, or thing.
This information is not essential to understand the sentence. The clause contains an additional, interesting detail.

👉 We always use commas with non-defining relative clauses.
👉 We NEVER use “that” in non-defining clauses.

What Is a Non-Defining Relative Clause?

A non-defining relative clause:

• gives extra information
• is separated with commas
• uses relative pronouns like who, which, where, when, whose
• can be removed and the sentence still makes sense

How to Form Non-Defining Relative Clauses

Non-defining relative clauses give extra information about a person, place, or thing.
This information is not essential to understand the main idea.
We always use commas to separate the extra information.

1. Structure

Main clause, relative pronoun + extra information, rest of the sentence.

2. Common Relative Pronouns (for Non-Defining Clauses)

Relative Pronoun	Used For	Example
who	people	My English teacher, who is from Canada, is very friendly.
which	things / animals	The book, which I finished yesterday, was fantastic.
where	places	Vancouver, where my cousins live, is beautiful.
when	times	2010, when I finished high school, was an important year for me.
whose	possession	Anna, whose car broke down, arrived late.

📝 Important:

Always add a comma before and after the clause (unless it ends the sentence).

Don’t use “that” in non-defining clauses.

3. Comma Rules

• Put a comma before and after the non-defining relative clause
  (unless it’s at the end of the sentence; then you only need one comma).

4. Key Points for Low-Level Learners

• You can remove the extra information and the sentence still makes sense.
• The verb form inside the clause follows normal grammar rules.
• Do not use these clauses to identify someone/something.
  (Those are defining clauses.)

Examples:

• My brother, who lives in Mexico, is visiting next month.
  (extra info: he lives in Mexico)
• The Eiffel Tower, which is in Paris, is very popular.
  (extra info: its location)
• September, when the weather is mild, is my favorite month.
  (extra info: weather in September)
• Chichén Itzá, where millions of tourists go each year, is amazing.
  (extra info: visitors)

🧠 Compare: Defining vs. Non-Defining

Type	Purpose	Example	Commas?	Use “that”?
Defining	Necessary information	The man who works here is kind. The man that works here is kind.	❌ No	✔ Yes
Non-defining	Extra information	My uncle Bob, who works here, is kind.	✔ Yes	❌ No

Defining Relative Clauses

Let’s Practice

Practice 1

Practice 2

Speaking

Practice 1

BOARD GAME

Sometimes we don’t know the facts, but we can make guesses or deductions about what’s true.
In English, we use modal verbs like may, might, could, must, and can’t to do this.
They help us show how sure or unsure we are about something.

Talking About Possibility

When we aren’t sure, but we think something is possible, we use may, might, or could + base form (the base form of the verb, without to).

These modals all mean “maybe”. They show that we’re guessing, not stating a fact.

💭 Examples of Possibility

💬 Sentence	💡 Meaning
She may be ill.	Maybe/ It’s possible she’s ill.
She might be lost.	Maybe/ It’s possible she’s lost.
She could be from another country.	Maybe/ It’s possible she’s is from another country.
She might not be here tomorrow.	Maybe/ It’s possible she won’t come tomorrow.

🎯 Quick Notes

• may, might, and could all express the same level of possibility.
• To make a negative, add not: might not / may not.

Example: He might not come to class today.

• They’re followed by a base form verb

✅ She might be late. ✖️ She might to be late.

🌦 Think of it like this:

Modal	How sure are you?	Example
may / might / could	🤔 Maybe yes, maybe no	It might rain later.

They’re your “maybe modals”

These modals are perfect when you’re not 100% sure, but something is possible!

Talking About Strong Possibility

Sometimes things look or sound true, even if we aren’t completely certain.
In this case, we use seem + to + verb to show a strong possibility or something that appears or feels true.

Think of it as saying:

“It looks like…” or “It sounds like…”

💭 Examples of Strong Possibility

💬 Sentence	💡 Meaning
She seems to be very cold.	It looks like she’s cold.
They seem to know each other well.	It appears they know each other.
This café seems to be popular.	It looks busy — probably true.
He seems to be tired.	It looks that way — I’m quite sure.

🧩 Grammar Pattern

seem + to + verb (base form)

✅ She seems to be tired.
✅ It seems to work well.

🌟 Remember

• “Seem” is stronger than may, might, or could.
• You use it when something looks or feels true, but you don’t have proof.
• It’s a polite, soft way to make an observation.

🎯 Compare

Expression	Meaning	Example
may / might / could	possible, not sure	She might be cold.
seem (to)	strong possibility	She seems to be cold.

Talking About Certainty

When you feel quite certain about something or you have good evidence or a strong reason, use must + verb.

It means you are almost 100% sure something is true.

💭 Examples of Deduction (Strong Certainty)

💬 Sentence	💡 Meaning
She must work at McDonald’s.	I’m almost sure. She is wearing a uniform.
He must be tired after the trip.	I’m almost sure. He traveled all night.
You must know her.	I’m sure it’s true. You work in the same office!
That must be our bus.	I’m certain — it’s the right number.

🧩 Grammar Pattern

must + verb (base form)

✅ She must be at work.
✅ He must live nearby.

🧠 Remember

• Use must when you see evidence or know facts that make something very likely.
• It’s much stronger than may, might, or could.
• Don’t use it for the past. This form talks about the present.

🎯 Compare

Expression	Meaning	Example
may / might / could	possible	He might be tired.
seem (to)	strong possibility	He seems to be tired.
must	sure, strong evidence	He must be tired.

Talking About Something is Impossible

When you are certain something is impossible, use can’t + verb.
It shows you are sure that your guess or idea is not true.

Think of it like saying:

“That’s impossible!” or “No way!”

💭 Examples of Deduction (Strong Negation)

💬 Sentence	💡 Meaning
She can’t be at work	I’m sure she isn’t. Her car is still here.
That can’t be his house.	Impossible. It’s too big!
He can’t know the answer	I’m certain he doesn’t. He didn’t come to class.
You can’t be serious!	I don’t believe it. It’s not true.

🧩 Grammar Pattern

can’t + verb (base form)

✅ He can’t be at school — it’s Sunday.
✅ That can’t be real!

🧠 Remember

• Use can’t when you are sure something isn’t true.
• It’s the opposite of must.
• Both talk about deduction in the present — what we think now.

⚖️ Compare

Expression	Meaning	Example
must	sure it’s true	She must be tired. (I’m almost sure she is tired)
can’t	sure it’s not true. It’s impossible	She can’t be tired. She just woke up! (It’s impossible she is tired)

🧠 Grammar Focus

Here’s a complete overview of the modals and expressions we use to talk about possibility, certainty, and impossibility:

Expression	Form	Example	Meaning
may	may + verb	She may be ill.	It’s possible.
might	might + verb	She might be lost.	It’s possible.
could	could + verb	He could be from another country.	It’s possible.
seem	seem + to + verb	She seems to know the answer.	It appears to be true.
must	must + verb	He must be tired after the long trip.	I’m almost certain this is true.
can’t	can’t + verb	That can’t be true!	I’m certain this is impossible.

Let’s Practice

Practice 1

Practice 2

Speaking