How to add extra information with commas, who and which
Short answer: Extra information gives a fact about a person or thing that the reader already knows. Put it between two commas and start it with who for a person or which for a thing: Ben, who lives next door, is my friend. Never use that between commas. The sentence must still make sense without the extra part.
🎯 I can add extra information with commas.
At a glance
| Pattern | Example |
|---|---|
| person: , who ... , | Ben, who lives next door, is my friend. |
| thing: , which ... , | Our school, which is very old, has a big garden. |
| needed information: no commas | The girl who has a kite is my sister. |
How to write it
- Write a clear sentence: Ben is my friend.
- Think of one extra fact: Ben lives next door.
- Add it between two commas with who or which.
- Take the extra part out and check that the sentence is still complete.
Rewrite practice
- Before:
Mia is my cousin. She is ten.
After: Mia, who is ten, is my cousin.
who adds an extra fact about a person. - Before:
Our house is new. It has a red door.
After: Our house, which has a red door, is new.
which adds an extra fact about a thing. - Before:
My sister plays chess. She is a nurse.
After: My sister, who is a nurse, plays chess.
Two commas around the extra part.
Common mistakes
My dog, that is brown, likes milk.→ My dog, which is brown, likes milk.
Never use that between commas.Paris, which is the capital of France is beautiful.→ Paris, which is the capital of France, is beautiful.
Close the extra part with a second comma.My bike, who is red, is old.→ My bike, which is red, is old.
A bike is a thing: use which.
Needed information and extra information
Needed information tells which one you mean and has no commas.
| Type | Example | Commas |
|---|---|---|
| needed | My brother who is ten plays chess. (I have more than one brother) | none |
| extra | My brother, who is ten, plays chess. (I have one brother) | two |
Check yourself
- Add commas: “Ben who lives next door is my friend.”
Show the answer
Ben, who lives next door, is my friend. Two commas.
- Choose: “My bike, ___ is red, is old.” (who / which)
Show the answer
which A bike is a thing.
- Fix: “My dog, that is brown, likes milk.”
Show the answer
My dog, which is brown, likes milk. No that between commas.
Rule cards that help
- Extra information with commas: Extra information goes between two commas. Use who for people and which for things. Never use that between commas.
Questions
How do I know if I need commas?
Ask whether the clause tells which one or only adds a fact. If the reader already knows which, use commas.
Why not that?
That is for needed information. For extra information, use who or which.
Where is the rule?
See the rule article on extra information with commas.
Part of 🌉 Because, when, if, who and more (stone 2 of the Learning Path). See also the English writing guide. Đọc bằng tiếng Việt.
Written for English learners by the English for Fun team. How we write our lessons · Last updated 2026-11-05.
Reviewed by Chinh Q. Hoang, PhD, founder, English for Fun · 2026-10-30
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