❌ Avoid this: The laptop, that I bought yesterday, is already updated.
✅ Use this: The laptop, which I bought yesterday, is already updated.
Use that when the clause is essential to the meaning of the sentence. Use which when the clause adds extra information that can be removed without changing the main meaning. The simple rule is this: that identifies; which adds.
That vs Which: The Simple Rule
A relative clause gives more information about a noun. The words that and which often introduce these clauses, but they do not work the same way in careful edited English.
- Use that for a restrictive clause: information the sentence needs.
- Use which for a nonrestrictive clause: information the sentence can live without.
- Use commas around a nonrestrictive which clause.
- Do not use commas around a restrictive that clause.
Restrictive: The files that are marked final should be sent today.
Nonrestrictive: The files, which are marked final, should be sent today.
What Is a Restrictive Clause?
A restrictive clause limits or identifies the noun before it. Without the clause, the reader may not know which person, thing, place, or idea you mean.
Use that for this kind of clause, especially in American English and in clear business, academic, and web writing.
✅ Correct Restrictive Use
The course that starts on Monday is full.
The phrase that starts on Monday tells us which course. It is needed, so there are no commas.
❌ Weak or Confusing Use
The course, that starts on Monday, is full.
The commas make the clause look extra, but that is not normally used this way in edited English.
More Restrictive Clause Examples
- The car that is parked outside belongs to my brother.
- The email that contains the invoice was sent yesterday.
- The article that explains the rule is easy to read.
- The shoes that fit best are on the top shelf.
In each sentence, the that clause answers a clear question: Which one? Which car? Which email? Which article? Which shoes?
What Is a Nonrestrictive Clause?
A nonrestrictive clause adds extra detail. The sentence still makes sense if you remove the clause. In this case, use which and put the extra information between commas.
✅ Correct Nonrestrictive Use
My phone, which I bought last year, still works well.
The main idea is My phone still works well. The clause adds extra detail, so which and commas are correct.
❌ Wrong Word Choice
My phone, that I bought last year, still works well.
When the information is extra and separated by commas, which is the natural choice.
More Nonrestrictive Clause Examples
- Our office, which is near the station, opens at nine.
- The report, which includes new charts, is ready for review.
- Her bicycle, which has a red basket, is easy to spot.
- The website, which loads quickly, gives a better reading experience.
Notice the punctuation. A which clause often needs a comma before it and a comma after it when it appears in the middle of a sentence.
Restrictive vs Nonrestrictive: Side-By-Side Examples
| Sentence Type | Example | Meaning | Punctuation |
|---|---|---|---|
| Restrictive | The books that have blue covers are on sale. | Only the blue-covered books are on sale. | No commas |
| Nonrestrictive | The books, which have blue covers, are on sale. | All the books are on sale, and they happen to have blue covers. | Commas needed |
| Restrictive | The apps that use less battery are better for travel. | Only certain apps are being discussed. | No commas |
| Nonrestrictive | This app, which uses less battery, is better for travel. | The app is already identified; the battery detail is extra. | Commas needed |
The Comma Test
The easiest way to choose between that and which is to test whether the clause can be removed.
- Remove the clause from the sentence.
- Read the sentence again.
- Ask: Does the sentence still identify the noun clearly?
If the sentence becomes unclear, use that with no commas. If the sentence still works and the clause only adds detail, use which with commas.
Example With the Comma Test
Original: The jacket that has silver buttons is mine.
Remove the clause: The jacket is mine.
Problem: Which jacket? The sentence may not be clear. The clause is needed, so that is correct.
Original: My jacket, which has silver buttons, is mine.
Remove the clause: My jacket is mine.
Result: The noun is already identified by my jacket. The clause is extra, so which is correct.
When That Is the Better Choice
Choose that when the clause is part of the basic meaning. It narrows the noun and helps the reader know exactly what you mean.
Use That After General Nouns
- The idea that works best is the simplest one.
- The option that saves time is worth choosing.
- The answer that matches the question is correct.
Use That When More Than One Thing Is Possible
If the noun could point to several people or things, a that clause helps the reader pick the right one.
- The student that submitted the form early received a confirmation email.
- The folder that contains the images is on the desktop.
- The room that faces the garden gets more sunlight.
For people, many writers prefer who instead of that: The student who submitted the form early… Both are often understood, but who sounds more natural for people.
When Which Is the Better Choice
Choose which when the clause gives a side note, not the main identification. The noun is already clear before the clause appears.
Use Which After a Clearly Identified Noun
- My laptop, which is almost five years old, still starts quickly.
- Sarah’s apartment, which is on the third floor, has a small balcony.
- The main entrance, which faces the street, is open during the day.
Use Which for Extra Comments About a Whole Idea
Sometimes which refers not just to a noun, but to the whole idea before it.
- The meeting ended early, which surprised everyone.
- The train arrived on time, which made the trip easier.
- She finished the draft today, which saved us time.
In these sentences, which comments on the full situation. That would not work naturally in this structure.
That vs Which in American and British English
In American English, many editors prefer that for restrictive clauses and which for nonrestrictive clauses. This rule keeps the sentence clean and easy to follow.
In British English, which is often used in restrictive clauses too, especially in everyday writing. For example, The book which explains the rule is on my desk may sound natural to many British readers.
For clear international web writing, the safest pattern is: that for essential information, which for extra information with commas.
Common Mistakes With That and Which
Mistake 1: Using That With Commas
❌ The camera, that I use for work, is in my bag.
✅ The camera, which I use for work, is in my bag.
Because the clause is set off with commas, it is extra information. Use which, not that.
Mistake 2: Adding Commas Around an Essential That Clause
❌ The password, that works, is written on the note.
✅ The password that works is written on the note.
The phrase that works tells us which password. It is essential, so it should not be separated with commas.
Mistake 3: Using Which Without Checking the Meaning
Possible but less direct: The documents which need signatures are on the desk.
Clearer in edited American English: The documents that need signatures are on the desk.
When the clause identifies which documents, that gives a cleaner signal to the reader.
Meaning Changes When You Switch That and Which
A small word can change the meaning. Look at this pair:
Restrictive Meaning
The shirts that are on the left are discounted.
Only the shirts on the left are discounted. The clause limits the noun.
Nonrestrictive Meaning
The shirts, which are on the left, are discounted.
All the shirts are discounted. Their location is just extra information.
This is why punctuation matters. Commas tell the reader whether the detail is part of the main meaning or just added information.
That vs Which Decision Table
| Question | Use | Example |
|---|---|---|
| Does the clause identify the noun? | That | The tab that is open needs to be saved. |
| Can the clause be removed without changing the main meaning? | Which | The tab, which is open, needs to be saved. |
| Are there commas around the clause? | Which | The printer, which is in the hall, is out of paper. |
| Would the sentence become unclear without the clause? | That | The printer that is in the hall is out of paper. |
How to Fix Sentences With That and Which
To fix a sentence, first decide whether the clause is essential or extra. Then choose the word and punctuation together.
Fix 1
❌ The restaurant, that serves fresh pasta, is closed today.
✅ The restaurant, which serves fresh pasta, is closed today.
The restaurant is already identified. The pasta detail is extra, so which works with commas.
Fix 2
❌ The restaurant, which serves fresh pasta, is closed today.
✅ The restaurant that serves fresh pasta is closed today.
This version means there may be more than one restaurant, and the fresh-pasta detail identifies the correct one. No commas are needed.
Fix 3
❌ The update which fixed the login issue is installed.
✅ The update that fixed the login issue is installed.
The clause identifies which update. In clean edited English, that is the better choice.
Mini Practice: Choose That or Which
Read each sentence and decide whether the missing word introduces essential or extra information.
| Sentence | Answer | Reason |
|---|---|---|
| The chair ___ has a broken leg should be repaired. | that | The clause identifies the chair. |
| My chair, ___ has a broken leg, should be repaired. | which | The chair is already identified by my. |
| The message ___ arrived this morning is important. | that | The clause tells us which message. |
| The message, ___ arrived this morning, is important. | which | The arrival time is extra information. |
Simple Memory Tip
That Identifies. Which Adds.
If the clause tells the reader which one, use that. If the clause adds a side detail, use which with commas.
Frequently Asked Questions
Can Which Be Used in a Restrictive Clause?
Yes, especially in British English and in less formal writing. Still, for clear edited English, especially for a mixed audience, that is the cleaner choice for restrictive clauses.
Do I Always Need a Comma Before Which?
No. A comma before which depends on meaning. Use commas when the which clause is extra: The laptop, which is new, runs quietly. If the clause identifies the noun, some writers use which without commas, but that is often clearer.
Can I Use That After a Comma?
In standard edited English, avoid using that after a comma to introduce a nonrestrictive clause. Use which instead.
Is That Only for Things?
No. That can refer to things, groups, and sometimes people. For people, who often sounds more natural: The teacher who helped me was kind.
What Is the Fastest Way to Choose?
Ask one question: Does this clause identify the noun? If yes, use that. If no, use which with commas.
