How to write with so that, who, which and that
Short answer: So that gives the purpose of an action: I wear a helmet so that I stay safe. Who, which and that add information about a noun: who for people, which for things and animals, and that for people, things and animals. Use that when you are not sure. Do not repeat the noun after them.
🎯 I can say a purpose and add information with who, which, that.
At a glance
| Word | Job | Example |
|---|---|---|
| so that | purpose | I came early so that I could sit near the front. |
| who | adds information about a person | The girl who sings is my sister. |
| which | adds information about a thing or animal | The bag which is on the chair is mine. |
| that | person, thing or animal | The book that I read was long. |
How to write it
- For a purpose, write the action, then so that and a full idea.
- To describe a noun, write the noun, then who, which or that and the extra information.
- Do not repeat the noun: the book that I read, not that I read it.
- Choose who for people, which for things; use that if unsure.
Rewrite practice
- Before:
I study hard. I want to pass the test.
After: I study hard so that I can pass the test.
so that gives the purpose. - Before:
I know a girl. She speaks three languages.
After: I know a girl who speaks three languages.
who joins a sentence about a person. - Before:
The cup is on the table. It is mine.
After: The cup that is on the table is mine.
that joins a sentence about a thing.
Common mistakes
The book that I read it was long.→ The book that I read was long.
that already means the book.The girl which sings is my sister.→ The girl who sings is my sister.
For people, use who.I study so that pass.→ I study so that I can pass.
so that needs its own subject.
Who, which and that
All three add information about a noun.
| Noun | Word | Example |
|---|---|---|
| person | who / that | the teacher who reads |
| thing | which / that | the book that I read |
| animal | which / that | the dog that barks |
Check yourself
- Choose: “The woman ___ lives here is a doctor.” (who / which)
Show the answer
who A woman is a person.
- Choose: “The cup ___ is on the table is mine.” (who / that)
Show the answer
that A cup is a thing.
- Fix: “The book that I like it.”
Show the answer
The book that I like. Do not repeat the noun.
Rule cards that help
- Why we do things: to and so that: To give a reason for an action, use to + the plain action word. so that can be followed by a full idea.
- Describing people with who: who adds information about a person. It takes the place of he or she, so do not say it twice.
- Describing things with that and which: that and which add information about a thing. Do not say the thing twice.
Sounds that help
- Rhythm & Chunking: who / which parts are one chunk
Questions
Can I leave out “that”?
Sometimes, when that is the object: the book I read. Keep it when it is the subject.
When do I use “so that”?
Use it for the purpose of an action, often with can or could: so that I can see.
Where are the rules?
See the rule articles for who and for that and which.
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