Punctuating Adjective Clauses: When to Use Commas
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- 5 min read
Punctuating Adjective Clauses — How to Know When to Use Commas
An adjective clause (relative clause) gives more information about a noun.It usually begins with 'who', 'whom', 'whose', 'which', 'that', 'where', or 'when'.
The key question is:
❓ Is the clause necessary to identify the noun, or is it just extra information?
🔹 STEP 1: Identify the Noun and the Clause
Structure:
Noun + relative pronoun + clause
Example:
The teacher who teaches English is kind.
Now decide: Is “who teaches English” necessary?
🔹 RULE 1: NO COMMA (Essential / Restrictive Clause)
✅ Use NO comma when the clause is necessary to identify which one.
Structural Clue:
If removing the clause changes the basic meaning or makes it unclear → NO comma
Pattern:
Common noun + who/that/which + identifying information
Examples:
1. The professor who teaches Chemistry 101 is excellent.(We need the clause to know which professor.)
2. The students who studied hard passed.(Not all students — only those who studied hard.)
3. The book that I bought yesterday is missing.
✔ Quick Test:
Remove the clause:
The professor is excellent.❌ Which professor? (Unclear)
So → NO comma
🔹 RULE 2: USE COMMAS (Nonessential / Nonrestrictive Clause)
✅ Use commas when the clause gives extra information only.
Structural Clue:
If removing the clause does NOT change the main meaning → Use commas
Pattern:
Proper noun + , who/which + extra info ,
OR
Specific person/thing already identified + , clause ,
Examples:
1. Professor Wilson, who teaches Chemistry 101, is excellent.(We already know who Professor Wilson is.)
2. Hawaii, which consists of eight islands, is beautiful.
3. Mrs. Smith, who is retired, volunteers here.
✔ Quick Test:
Remove the clause:
Professor Wilson is excellent.✔ Still clear.
So → Use commas
🔹 IMPORTANT STRUCTURAL CLUES
1️⃣ Proper Noun Rule
If the clause modifies a proper noun, use commas.
Structure:
Name + , who/which + info ,
Example:
Rahul, who lives in Delhi, is my friend.
2️⃣ “That” Rule
❗ “That” is NOT used in nonessential clauses.
So:
✔ The book that I bought is interesting.❌ The book, that I bought, is interesting. (Wrong)
If you see that, usually → NO comma
3️⃣ All vs Some Meaning Clue
Compare:
With commas:
The children, who wanted to play soccer, ran to the field.Meaning: ALL the children wanted to play.
Without commas:
The children who wanted to play soccer ran to the field.Meaning: Only SOME children wanted to play.
🔹 Mechanical Structure Summary
Structure Type | Comma? | Meaning |
Common noun + identifying clause | ❌ No comma | Necessary information |
Proper noun + clause | ✔ Comma | Extra information |
Clause with “that” | ❌ No comma | Essential clause |
Clause removable without confusion | ✔ Comma | Nonessential |
Clause needed to answer “Which one?” | ❌ No comma | Essential |
🔹 SIMPLE FORMULA
Ask yourself:
1️⃣ Can I remove the clause and still know exactly who/what it is?
→ YES → Use commas→ NO → Do not use commas
🔹 Quick Practice
1. My brother who lives in Mumbai is a doctor.(Do I have more than one brother?)
o If YES → No comma
o If only one → My brother, who lives in Mumbai, is a doctor.
🎯 Final Concept
There are only TWO types:
1. Essential (Restrictive)
No commasIdentifies the noun
2. Nonessential (Non-restrictive)
CommasAdds extra information
Necessary or Additional? (With Explanation)
We apply this rule:
Necessary (Essential) clause → NO commas
Additional (Nonessential) clause → Use commas
Ask yourself: Does the clause identify which one? Or is it just extra information?
1. The woman who runs the local bakery makes the best sourdough bread.
✅ No commas
Why? The clause identifies which woman. Without it, we don’t know which woman makes the bread.
2. Yes, Michael is on the basketball team. But Sarah Jenkins, who transferred here last semester, is the captain of the debate club.
✅ Commas added
Why? “Sarah Jenkins” is a proper noun. We already know who she is. The clause gives extra information.
3. Water, which covers most of the Earth's surface, is essential for all living things.
✅ Commas added
Why? This applies to water in general. This is general knowledge, not identifying a specific puddle or glass of water. Remove clause: Water is essential... (Still clear)
4. The water that I left in my car all day is too warm to drink.
✅ No commas
Why? It identifies which water (specifically the water left inside the car, not water in general).
5. The documentary focused on a scientist who discovered a new species of frog.
✅ No commas
Why? It identifies which scientist the documentary was about.
6. Marie Curie, who won two Nobel Prizes, was a pioneer in the field of radioactivity.
✅ Commas added
Why? Marie Curie is a specific person (proper noun). The clause adds extra, nonessential information about her achievements.
7. I am planning a surprise party for my mother, who is turning sixty next week.
✅ Commas added
Why? You only have one mother in this context. Because her identity is already established by her relationship to you, the clause is additional information.
8. I want to buy a car that gets excellent gas mileage.
✅ No commas
Why? There are millions of cars. The clause is necessary to identify exactly which type of car you want.
9. Students who skip lectures will struggle with the final exam.
✅ No commas
Why? It identifies exactly which students will struggle (not all students, only the ones who skip).
10. In the famous novel, Harry Potter, who discovered he was a wizard on his eleventh birthday, eventually defeated the Dark Lord.
✅ Commas added
Why? Harry Potter is a specific, known character (proper noun). The clause gives extra background information about him.
✅ Final Answers (Clean Version)
1. The woman who runs the local bakery makes the best sourdough bread.
2. Sarah Jenkins, who transferred here last semester, is the captain of the debate club.
3. Water, which covers most of the Earth's surface, is essential for all living things.
4. The water that I left in my car all day is too warm to drink.
5. The documentary focused on a scientist who discovered a new species of frog.
6. Marie Curie, who won two Nobel Prizes, was a pioneer in the field of radioactivity.
7. I am planning a surprise party for my mother, who is turning sixty next week.
8. I want to buy a car that gets excellent gas mileage.
9. Students who skip lectures will struggle with the final exam.
10. In the famous novel, Harry Potter, who discovered he was a wizard on his eleventh birthday, eventually defeated the Dark Lord.
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