That or Which: Difference and When Should You Use Each?

Both flutist and flautist are correct, but flutist is more common in American English, while flautist is used more often in British English and classical music contexts.

Have you ever stopped while writing and wondered, should I use that or which? You are not alone. Many English learners, students, and even native speakers get confused by these two small words. They look similar because both introduce extra information, but they are not always used the same way.

Understanding that or which can make your writing clearer and more professional. It also helps you avoid grammar mistakes in school assignments, emails, blogs, and business writing. While the difference is simple once you know the rule, many people still use them incorrectly because everyday speech often ignores the distinction.

The good news is that learning when to use that and which is easier than you think. This guide explains the difference in simple English, provides real-life examples, and shows you the grammar rules used in American and British English. By the end, you’ll know exactly which word fits your sentence and write with greater confidence.

That or Which – Quick Answer

The main difference is simple:

• That introduces essential information. The sentence would lose its meaning without it.
• Which introduces extra information that can be removed without changing the main meaning. It is usually set off with commas.

Examples

• The book that I borrowed is excellent.
• My laptop, which I bought last year, still works perfectly.
• The students that arrived early got the best seats.

Quick tip: If the information is necessary, use that. If it is extra information, use which.

The Origin of That or Which

Both words have been part of English for hundreds of years.

That comes from Old English and has long been used as a demonstrative word and a relative pronoun. It points to a specific person or thing.

Which comes from Old English as well, originally meaning “what one” or “which one.” Over time, it became a relative pronoun used to add more information.

The modern grammar rule separating that and which became more popular in the 20th century, especially in American English. Many style guides recommend using that for restrictive clauses and which for non-restrictive clauses.

In everyday conversation, people often mix them, but formal writing usually follows this distinction.

British English vs American English Spelling

Unlike many English words, that and which have no spelling differences between British and American English. The words are spelled exactly the same.

The main difference is usage style, not spelling.

Version	Spelling	Region	Example Sentence
American English	That	United States	The phone that I bought is new.
American English	Which	United States	My phone, which is new, works well.
British English	That	United Kingdom	The car that I drive is blue.
British English	Which	United Kingdom	The car, which is blue, is parked outside.

British English is sometimes more flexible in allowing which where American English strongly prefers that.

Which Spelling Should You Use?

Since there is no spelling difference, the choice depends on grammar.

For a US Audience

Follow the standard grammar rule:

• Use that for essential information.
• Use which with commas for extra information.

For a UK or Commonwealth Audience

The same rule is recommended, although British writers may occasionally use which in places where Americans would choose that.

For Global or SEO Writing

Following the American style guide makes your writing clear for most readers worldwide.

When in doubt:

• Essential information → that
• Extra information → which

Common Mistakes with That or Which

Many learners make these mistakes.

Incorrect	Correct
The movie, that I watched, was great.	The movie that I watched was great.
My car which is red needs washing.	My car, which is red, needs washing.
The dog, that barked, ran away.	The dog that barked ran away.
My teacher that lives nearby is helpful. (if extra information)	My teacher, which lives nearby… ❌ (Use who for people.)

Remember

• Don’t use which without commas when adding extra information.
• Don’t use which instead of who for people.
• Use commas with non-essential which clauses.

That or Which in Everyday Examples

Emails

• Please send the report that you finished yesterday.
• I received your email, which answered all my questions.

News Headlines

• Company launches product that improves battery life.
• Museum opens exhibition, which features rare artwork.

Social Media

• I finally found the recipe that everyone loves!
• This café, which just opened, is amazing.

Formal Writing

• The proposal that meets all requirements will be accepted.
• The final report, which includes updated research, was published today.

That or Which – Google Trends & Usage

Searches for that or which remain popular because many people struggle with English grammar.

Users from the United States often search for grammar rules that explain the difference between restrictive and non-restrictive clauses. In the United Kingdom, Australia, Canada, and other English-speaking countries, learners also frequently search for this topic.

Students, bloggers, content writers, and professionals commonly look up that or which when proofreading documents or preparing formal writing.

Because this grammar rule appears in many style guides, it continues to be one of the most searched English grammar topics.

Comparison Table

Feature	That	Which
Purpose	Essential information	Extra information
Commas Needed	No	Yes, usually
Formal Writing	Preferred for restrictive clauses	Preferred for non-restrictive clauses
American English	Strongly recommended	Used for extra details
British English	Common	More flexible
Can Information Be Removed?	No	Yes

FAQs

Is it better to use that or which?

It depends on the sentence. Use that for necessary information and which for additional information.

Can I replace that with which?

Sometimes, but not always. In formal American English, each has a different grammatical role.

Does British English use which more often?

Yes. British English can be slightly more flexible, although the standard grammar rule still applies.

Do I need commas with which?

Usually yes. A which clause that adds extra information is normally enclosed by commas.

Is that or which a spelling difference?

No. Both words have the same spelling worldwide. The difference is grammatical.

Which is more common in formal writing?

Both are common, but each is used in different situations according to grammar rules.

Can I ignore the rule in casual writing?

In casual conversation, people often mix them. In formal writing, following the rule makes your writing clearer.

Conclusion

Choosing between that or which does not have to be difficult. The key is understanding whether the information in your sentence is essential or simply adds extra detail. If the sentence cannot make sense without the information, use that. If the information is additional and can be removed without changing the main meaning, use which with commas.

There is no spelling difference between British and American English, but American style guides usually apply the grammar rule more strictly. Following this rule will improve your essays, emails, reports, and online content while making your writing easier to read.

Whenever you pause and wonder about that or which, ask yourself one simple question: Is this information necessary? Your answer will guide you to the correct choice. With a little practice, using these two words correctly will soon become second nature.

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