Which vs. That becomes much easier to understand once you know how each word works in English grammar. From my own editing experience, learning when to use Which or That made my writing much stronger and easier to read. Every writer, experienced writers, and anyone improving written communication can benefit from this comprehensive guide. It includes a clear explanation, practical grammar tips, useful writing tips, and real examples that explain the difference, differences, meaning, sentence meaning, sentence meanings, additional information, essential information, nonessential information, details, essential details, nonessential details, context, contextual clues, purpose, and proper usage.
It also explains how a relative pronoun introduces a relative clause, restrictive clause, nonrestrictive clause, defining clause, nondefining clause, clause, or clauses that add, affect, restrict, or change the meaning of a word or complete message.As you learn, continue learning, and know the rule, you can choose the right choice, write correctly, improve clarity, strengthen readers’ understanding, and communicate more confidently.Many learners experience confusion because both words look similar, yet each has a different role.
Following a grammar rule and proper punctuation helps you understand why a comma and a parenthetical phrase belong with a nonrestrictive clause, while a restrictive clause normally appears without commas.This distinction is important, often crucial, and provides useful clarification for essential and nonessential information.If you feel unsure, have paused, or have wondered whether one choice is correct, read on.The guide includes dozens of examples and shows how incorrect choices reduce accuracy, readability, and make proofreading, editing, and revision more difficult.
Which vs. That: What’s the Difference?
The main difference between which and that lies in how important the information is to the sentence.
- That introduces essential (restrictive) information.
- Which introduces nonessential (nonrestrictive) information.
In other words:
- Use that when the information is necessary to identify exactly what you’re talking about.
- Use which when the information simply adds extra detail that could be removed without changing the sentence’s basic meaning.
Consider these examples.
Using “that”:
The laptop that has the blue sticker belongs to Sarah.
The phrase that has the blue sticker identifies which laptop belongs to Sarah. Without it, the sentence becomes unclear because there could be several laptops.
Using “which”:
The laptop, which has a blue sticker, belongs to Sarah.
Here, the speaker already assumes everyone knows which laptop they’re discussing. The blue sticker is just extra information.
This small distinction changes both grammar and meaning.
Quick Comparison Table: Which vs. That
| Feature | That | Which |
| Clause Type | Restrictive (essential) | Nonrestrictive (nonessential) |
| Information | Required | Extra |
| Commas | No commas | Uses commas |
| Can sentence work without clause? | Usually no | Yes |
| Common in formal writing | Yes | Yes |
| Common in casual writing | Yes | Yes |
What Are “Which” and “That” in Grammar?
Before learning the rules, it helps to understand what these words actually are.
Both which and that often function as relative pronouns. A relative pronoun introduces a relative clause, which describes or identifies a noun.
For example:
The book that I bought is fascinating.
The clause tells you which book.
Another example:
The book, which I bought yesterday, is fascinating.
This clause simply adds more information.
Although both words introduce clauses, they don’t introduce the same kind of clause.
Parts of Speech
Depending on the sentence, which and that can serve different grammatical functions.
| Word | Possible Parts of Speech |
| Which | Relative pronoun, interrogative pronoun, determiner |
| That | Relative pronoun, conjunction, determiner, pronoun, adverb |
Examples:
👉Which as a Question Word
Which movie do you want to watch?
Which as a Relative Pronoun
The movie, which won several awards, is now streaming.
That as a Relative Pronoun
The movie that won several awards is now streaming.
That as a Conjunction
I know that she’s coming tomorrow.
Notice that not every use of “that” follows the which-vs-that rule. The rule only applies when both words function as relative pronouns.
Understanding Restrictive and Nonrestrictive Clauses
This is the rule that matters most.
Everything else builds on this idea.
What Is a Restrictive Clause?
A restrictive clause contains information that identifies the noun.
Without it, the sentence loses its intended meaning.
Examples:
Students that arrive late must sign in.
Which students?
Only the late ones.
Without the clause:
Students must sign in.
Now every student must sign in, which changes the meaning.
More examples:
- The restaurant that serves Thai food closes at midnight.
- Cars that use electric power require less maintenance.
- Employees that complete the training receive certificates.
Each clause limits the noun.
That’s why that is used.
What Is a Nonrestrictive Clause?
A nonrestrictive clause adds interesting information.
You can remove it without changing the sentence’s basic meaning.
Example:
My brother, which lives in Seattle, enjoys hiking.
In American English, you’d normally use who for people, but notice the structure.
Removing the clause gives:
My brother enjoys hiking.
The sentence still identifies the subject perfectly.
Additional examples:
My car, which I bought last year, still looks brand new.
Remove the clause:
My car still looks brand new.
Nothing essential disappears.
Visual Comparison
| Restrictive Clause | Nonrestrictive Clause |
| Essential information | Extra information |
| Uses that | Uses which |
| No commas | Commas required |
| Changes meaning if removed | Doesn’t change meaning if removed |
Why Choosing Between Which and That Matters
Some people think the difference doesn’t matter.
In casual conversation, it often doesn’t.
However, in professional writing, journalism, publishing, academic papers, technical documentation, and business communication, correct usage improves clarity.
Consider these two sentences.
The employees that completed training received bonuses.
Only trained employees received bonuses.
Now compare:
The employees, which completed training, received bonuses.
Ignoring the incorrect use of which for people, the commas suggest all employees completed training.
The meaning changes completely.
That’s why editors pay close attention to restrictive and nonrestrictive clauses.
Benefits of Using Which and That Correctly
Using the correct word helps you:
- Write clearer sentences.
- Avoid ambiguity.
- Improve professional communication.
- Follow American English grammar conventions.
- Make your writing easier to edit.
- Build credibility with readers.
- Reduce misunderstandings.
Even if readers don’t consciously notice the grammar, they’ll usually find your writing smoother and easier to follow.
American English vs. British English
One reason people become confused is that American and British English don’t always follow the same convention.
American English
Most style guides recommend:
- That → restrictive clauses
- Which → nonrestrictive clauses
Example:
The computer that needs repairs is mine.
My computer, which needs repairs, is five years old.
British English
British English is more flexible.
Many British publications use which for both restrictive and nonrestrictive clauses, although that is also acceptable.
Example:
The car which I bought yesterday is electric.
This is common in British writing but less common in formal American English.
If you’re writing for an international audience, following the American distinction usually provides the clearest structure because readers immediately recognize whether the clause is essential.
Simple Rule to Remember
If you’re unsure which word to choose, ask yourself one question:
Can I remove this clause without changing the sentence’s meaning?
If the answer is yes, use which.
If the answer is no, use that.
Think of it like this:
- That identifies.
- Which describes.
It’s a simple memory trick that works surprisingly well in everyday writing.
Common Mistakes When Using Which vs. That
Even native English speakers confuse which vs. that. Most mistakes happen because the writer doesn’t know whether the information is essential or extra. Once you understand that difference, choosing the correct word becomes much easier.
Here are the mistakes people make most often and how to avoid them.
Using “Which” for Essential Information
One of the biggest errors is using which when the clause identifies exactly which person or thing you’re talking about.
Incorrect:
The laptop which has 32 GB of RAM runs smoothly.
Correct (American English):
The laptop that has 32 GB of RAM runs smoothly.
Without the clause has 32 GB of RAM, the reader wouldn’t know which laptop you mean. The information is essential, so that is the better choice.
Using “That” After a Comma
If you’ve added commas, you’re introducing extra information. In that case, use which, not that.
Incorrect:
My neighbor’s dog, that loves swimming, jumps into the lake every morning.
Correct:
My neighbor’s dog, which loves swimming, jumps into the lake every morning.
The sentence already identifies the dog. The fact that it loves swimming is simply additional information.
Forgetting Commas Around Nonrestrictive Clauses
Many writers choose which correctly but forget the punctuation.
Incorrect:
My bicycle which I bought last year is already rusting.
This sentence leaves readers wondering whether you own more than one bicycle.
Correct:
My bicycle, which I bought last year, is already rusting.
The commas tell readers the information is supplementary.
Adding Unnecessary Clauses
Sometimes a sentence becomes longer without becoming clearer.
Wordy:
The restaurant, which is located downtown, serves excellent pizza.
If the location isn’t relevant, simply write:
The restaurant serves excellent pizza.
Every clause should have a purpose. If removing it doesn’t change the meaning, consider removing it entirely.
Assuming British and American English Follow Identical Rules
This causes confusion for many learners.
In American English, editors generally recommend:
- Use that for restrictive clauses.
- Use which for nonrestrictive clauses.
In British English, writers often use which in restrictive clauses without it being considered incorrect.
American English
The movie that won the award deserves the praise.
British English
The movie which won the award deserves the praise.
Both versions are grammatically acceptable within their respective style conventions. However, if you’re writing for a U.S. audience, sticking to that for restrictive clauses improves consistency and readability.
Quick Editing Checklist for Which vs. That
Before publishing or submitting your writing, ask yourself these questions:
| Question | Use |
| Can I remove the clause without changing the sentence’s main meaning? | Which |
| Does the clause identify exactly which person or thing I’m talking about? | That |
| Does the clause have commas? | Which |
| Would removing the clause confuse the reader? | That |
| Am I writing for an American audience? | Prefer that for restrictive clauses |
This five-step check catches most mistakes in seconds.
Which vs. That in Different Types of Writing
The best choice also depends on what you’re writing.
| Writing Type | Preferred Usage |
| Academic papers | Follow the style guide (APA, MLA, Chicago) |
| Business writing | Prefer the American distinction between that and which |
| Journalism | Most U.S. news organizations follow the distinction consistently |
| Creative writing | Flexibility is acceptable if clarity remains strong |
| Blog posts | Use the distinction consistently to improve readability and SEO |
Professional editors appreciate consistency even more than perfection.
Which vs. That Memory Trick
If you only remember one rule, make it this one:
If you can remove the clause and the sentence still works, use “which.” Or if you can’t remove it, use “that.”
Examples:
The shoes that fit best are on sale.
You can’t remove that fit best, because readers won’t know which shoes you mean.
The shoes, which I bought yesterday, are already on sale.
You can remove which I bought yesterday, and the sentence still makes complete sense.
This simple test works in most everyday writing situations.
Conclusion
Understanding which vs. that is one of the simplest ways to improve your English writing. Although both words introduce additional information, they serve different purposes. That identifies essential information that cannot be removed, while which adds extra details that are usually separated by commas. Once you understand this distinction, it becomes much easier to choose the correct word and write clear, accurate sentences.
The more you practice using which and that in everyday writing, the more natural the rule becomes. Whether you are writing emails, school assignments, blog posts, business reports, or social media captions, applying the correct grammar rule improves clarity, readability, and your readers’ understanding. With a little practice, you can avoid common mistakes, communicate more confidently, and make every sentence more precise.
FAQs
Q1. What is the difference between which and that?
That introduces essential information that defines the noun, while which introduces additional, nonessential information that can usually be removed without changing the sentence’s core meaning.
Q2. When should I use “that” instead of “which”?
Use that when the information is necessary to identify the person, place, or thing you are talking about. Restrictive clauses introduced by that generally do not use commas.
Q3. When should I use “which”?
Use which when adding extra information that is helpful but not essential. Nonrestrictive clauses introduced by which are usually separated by commas.
Q4. Do I always need a comma before “which”?
In most cases, yes. When introducing a non-restrictive clause, place a comma before it. However, there are exceptions depending on the writing style or regional conventions.
Q5. Can “which” and “that” be used interchangeably?
Sometimes they can, but not always. Replacing one with the other may change the meaning or make the sentence grammatically incorrect.
