Table of Contents
- Key Pointers
- The Short Version
- So, what’s the actual rule for which vs that?
- Six example pairs to make which vs that stick
- The comma trick for testing which vs that
- Common exceptions and where the rule bends
- Mini quiz: which vs that
- Where the which vs that rule matters most
- Wrap-up
- FAQs
- Sign Up for Quetext Today!
Key Pointers
- The core rule: use “that” to introduce a restrictive clause (essential information, no commas). Use “which” to introduce a non-restrictive clause (extra information, set off with commas).
- Restrictive clause = the sentence needs it to make sense. Non-restrictive clause = the sentence still works without it.
- The comma is a giveaway. If the clause is set off by commas, “which” is correct. If it isn’t, “that” is correct.
- British English is looser about the rule than American English, but most style guides (APA, Chicago, AP) still follow it.
- Grammar checkers catch “which”/“that” misuse reliably. Running your draft through one before you submit is the fastest way to stop making the error.
The Short Version
Use “that” when the information after it is essential to the sentence’s meaning. Use “which” when the information is extra and separate it with commas. “The book that I borrowed is on my desk” tells you which specific book. “The book, which I borrowed from the library, is on my desk” adds extra detail you could delete without breaking the sentence. If you can remove the clause and still have a complete thought, use “which” with commas. If you can’t, use “that.”
So, what’s the actual rule for which vs that?
Picture a Wednesday night. You’re finishing a report, and Word keeps underlining every “which” you type. Or your professor left a note in the margin: “use ‘that’ here.” You know the words are close in meaning, but you don’t quite know when to use which one. The rule is small, and once you see it, it stays with you.
Here’s the whole thing:
Use “that” for restrictive clauses. A restrictive clause is essential to the sentence. Remove it and the sentence loses meaning.
Use “which” for non-restrictive clauses. A non-restrictive clause adds extra information. Remove it and the sentence still makes sense.
The signal that tells you which one you’re using is punctuation. Restrictive clauses take no commas. Non-restrictive clauses are set off by commas.
The Purdue OWL on that vs which covers the rule concisely, and the APA Style guide on that versus which confirms it’s the standard in academic writing.
Six example pairs to make which vs that stick
Same idea, different clause types.
1.
- The car that is parked outside is mine. (Restrictive, tells you which car.)
- The car, which is parked outside, is mine. (Non-restrictive, extra detail; there’s only one car in context.)
2.
- The report that I finished last night is due today.
- The report, which I finished last night, is due today.
3.
- Employees that miss training must reschedule.
- All employees, which number about 200, receive annual training.
4.
- The book that she recommended changed how I write.
- The book, which she recommended, is on the syllabus.
5.
- I bought the phone that was on sale.
- I bought a new phone, which was on sale.
6.
- Every article that cites Smith uses the 2020 edition.
- Smith’s book, which was published in 2020, is widely cited.
In every pair, the “that” version restricts your meaning to a specific thing. The “which” version keeps the meaning general and adds extra detail on the side.
The comma trick for testing which vs that
If you can’t tell which one belongs, ask two questions:
- Can I delete the clause and keep the sentence? If yes → non-restrictive → use “which” with commas.
- Do I need the clause to know which thing I’m talking about? If yes → restrictive → use “that” without commas.
Example: “The laptop that I use for work is a MacBook.”
- Delete the clause: “The laptop is a MacBook.” That sentence is now vague. Which laptop?
- The clause is essential → restrictive → use “that.”
Same sentence flipped: “My work laptop, which I bought in 2023, is a MacBook.”
- Delete the clause: “My work laptop is a MacBook.” That still makes sense.
- The clause is extra → non-restrictive → use “which” with commas.
The UNC Writing Center on commas covers the broader comma rules for non-restrictive clauses, which is worth a read if the punctuation piece is where you keep slipping.
Common exceptions and where the rule bends
Two situations where the rule loosens.
British English is more relaxed. Many British publications use “which” for both restrictive and non-restrictive clauses without the comma distinction. The which/that rule is more strictly enforced in American English, especially in academic and professional writing.
Casual writing sometimes ignores it. Fiction, blogs, and everyday communication often use “which” restrictively without commas. It won’t stop the reader, but it will get flagged in formal contexts.
When “that” gets awkward. If you already have a “that” earlier in the sentence, using “which” for the second clause can read more smoothly. “I decided that the shirt, which was on sale, was worth buying.” Technically the rule allows swapping, but readability wins.
Mini quiz: which vs that
Pick the right word for each sentence. Answers below.
- The email _____ I sent yesterday hasn’t been answered yet.
- My new laptop, _____ I bought last week, is already causing problems.
- Any student _____ misses two classes must speak with the instructor.
- The Golden Gate Bridge, _____ opened in 1937, is a San Francisco landmark.
- The report _____ she wrote received top marks.
- Our marketing team, _____ has 12 members, meets every Monday.
Answers: 1. that, 2. which, 3. that, 4. which, 5. that, 6. which.
If you got 5 or 6 right, you’ve internalized the rule. If you missed a couple, look at whether commas surround the clause, that’s usually the tell.
Try this: Paste your draft into Quetext’s Grammar Checker and watch it flag which/that misuse in real time. The free tier covers the first 1,000 words, which is enough to spot-check most short essays or emails. If you’d rather start with a quick baseline pass, Quetext covers your first 1,000 words at no cost.
Where the which vs that rule matters most
Three settings where getting it right actually shows up in feedback.
Academic writing. Professors and academic editors follow the rule strictly. A misused “which” without commas is a small error that adds up across a paper.
Business and technical writing. Reports, memos, and documentation use the rule to keep meaning precise. Mixing them up can change what a sentence actually claims.
Professional emails. When you’re writing under time pressure, the wrong word slips in easily. The breakdown on mastering tone in email communication covers the broader email-writing patterns worth catching before you send.
For related grammar rules that trip up the same writers, our post on what is a dangling modifier covers another small structural issue that changes sentence meaning, and active voice vs passive voice covers the choice that shapes rhythm across the entire draft.
Wrap-up
“That” introduces essential information, no commas. “Which” introduces extra information, commas on both sides. If you can delete the clause and keep the sentence, use “which.” If deleting the clause would leave the reader confused, use “that.” The rule is small, the fixes are quick, and grammar checkers catch the error the moment you try to submit.
Fix which vs that errors instantly — try Quetext Grammar Checker free. The first 1,000 words are no-cost, which is enough for most short essays, emails, or blog drafts.
FAQs
When should I use “which” vs “that”?
Use the term “that” for restrictive clauses (meaning vital information where commas are not used). Use the term “which” if the clause is non-restrictive (meaning additional or extra information and the clause is separated by commas). In order to determine this, test by deleting the clause: if in the new sentence the clause may be omitted without any damage to the meaning of the original sentence, use “which” and make sure it is positioned with commas.
- Use “that” for restrictive clauses
- Use “which” for non-restrictive clauses
- Perform deletion test
Can “which” and “that” be used interchangeably?
In colloquial writing and British English, it is permissible to use the two terms interchangeably. In formal American English (in academic, professional, or journalistic writing), it is not allowed. Almost all of the well-known style guides, including APA, Chicago, and AP, apply the strictly formatted definition. Whenever you write an essay, business document, or other written work, one must follow this grammar rule to avoid getting one’s text edited.
- Casual and British English: interchangeable
- Formal American English: not interchangeable
- Style guides enforce the distinction
What’s a restrictive vs non-restrictive clause?
The restrictive clause plays an important role in the meaning of the sentence. If it is removed the sentence can become vague. The non-restrictive clause serves to provide information relevant to the sentence. The restrictive clause will always be linked to “that” and will not contain commas, while the non-restrictive clause will be linked to “which” and will be set off by commas.
- Restrictive: important, without commas, “that”
- Non-restrictive: provides unnecessary details, with commas, “which”
- The comma is the indicator
Does grammar-checking software catch which/that errors?
Indeed, the vast majority of contemporary grammar checking tools successfully identify problems associated with the usage of which and that. With Quetext, one can detect all the mistakes connected with the use of commas and this particular one simultaneously, which is probably the simplest and the fastest solution before submitting the paper. In case you are often making a mistake like that in your own writing, putting papers through a grammar checker for several weeks will create a good habit and one day you will be able to catch yourself making a mistake like that.
- Grammar checkers manage to identify mistakes with the use of which and that
- Quetext can identify various mistakes during the same scanning process
- Regular usage of the Grammarly tool will help you create good habits
