That vs Which: Restrictive & Non-Restrictive Clauses Guide

Introduction

Choosing between “that” and “which” can be one of the trickiest decisions in English grammar. Many native speakers mix them up, but if you are learning English at a B1 or B2 level, knowing the difference will instantly make your writing clearer and more professional. In this guide, you will learn the simple rule that separates these two words, see plenty of examples, and avoid common mistakes.

What Is the Difference Between “That” and “Which”?

Both “that” and “which” are relative pronouns. They introduce relative clauses—extra information about a noun in a sentence. The key difference is whether the information is essential (restrictive) or non-essential (non-restrictive).

• Restrictive clause (using that): The information is necessary to identify the noun. Without it, the sentence meaning changes.
• Non-restrictive clause (using which): The information is extra. You can remove it, and the sentence still makes sense. Non-restrictive clauses are always set off with commas.

Rules

1. Use “that” for restrictive (essential) clauses. Do not use commas. Example: The book that I borrowed is on the table. (Which book? The one I borrowed.)
2. Use “which” for non-restrictive (non-essential) clauses. Always add a comma before which (and a comma after the clause if it is in the middle of a sentence). Example: My car, which is blue, needs a wash. (The fact that it is blue is extra information.)
3. Never use “that” after a comma. If you see a comma before the relative pronoun, you must use which (or who for people).
4. Use “which” (not “that”) after prepositions. Example: The house in which I grew up is now a museum. (Not: The house in that I grew up…)
5. Use “that” (not “which”) after superlatives and words like “all,” “every,” “only,” “none,” and “no.” Example: This is the best cake that I have ever eaten.

How to Use It

Follow these three steps every time you write a sentence with a relative clause:

1. Identify the noun that the clause describes. Ask yourself: Is the clause necessary to know which noun I mean?
2. If yes → use “that” (no commas). Example: The students that study hard pass the exam. (Which students? The ones who study hard.)
3. If no → use “which” (with commas). Example: The students, which are in Room 5, study hard. (All students are in Room 5; it is extra information.)

Tip: Try removing the clause. If the sentence still gives the same main meaning, use which with commas. If the sentence becomes unclear or incomplete, use that without commas.

Examples in Sentences

• The laptop that I bought last week is already broken. (Restrictive: identifies which laptop.)
• My laptop, which I bought last week, is already broken. (Non-restrictive: I only have one laptop.)
• Dogs that bark loudly annoy the neighbours. (Restrictive: only the loud ones.)
• Dogs, which are loyal animals, make great pets. (Non-restrictive: all dogs are loyal.)
• The movie that won the Oscar is playing tonight. (Restrictive: which movie.)
• The movie, which is three hours long, is playing tonight. (Non-restrictive: extra detail about the movie.)
• She adopted the cat that had blue eyes. (Restrictive: there were other cats.)
• She adopted the cat, which had blue eyes. (Non-restrictive: only one cat.)
• I need a car that is fuel-efficient. (Restrictive: any fuel-efficient car.)
• My car, which is fuel-efficient, is perfect for long trips. (Non-restrictive: my only car.)
• The teacher that gave us extra homework is strict. (Restrictive: identifies the teacher.)
• The teacher, which is a common mistake here, should actually be “who” for people. (But note: for people, use “who” instead of “which.”)

Common Mistakes

1. Mistake: Using “which” without a comma for essential information.
   ❌ The car which I bought is red. (Missing comma, but if it is restrictive, use “that.”)
   ✅ The car that I bought is red. (Restrictive: you bought one of many cars.)
   ✅ The car, which I bought yesterday, is red. (Non-restrictive: you own only one car.)
2. Mistake: Using “that” after a comma.
   ❌ My house, that is old, needs repair.
   ✅ My house, which is old, needs repair.
3. Mistake: Forgetting the comma before “which” in non-restrictive clauses.
   ❌ The cake which was chocolate was delicious. (If you mean all cakes are chocolate, add a comma.)
   ✅ The cake, which was chocolate, was delicious.
4. Mistake: Using “which” for people.
   ❌ The woman which lives next door is friendly.
   ✅ The woman who lives next door is friendly. (Use “who” or “that” for people; “which” is for things and animals.)
5. Mistake: Using “that” after a preposition.
   ❌ The city in that I was born is small.
   ✅ The city in which I was born is small. (Or: The city that I was born in is small.)

Quick Summary

• Restrictive clause (essential): Use that. No commas. Example: The phone that has a cracked screen is mine.
• Non-restrictive clause (non-essential): Use which. Add commas. Example: My phone, which has a cracked screen, is still working.
• For people, use who or that (avoid which).
• After prepositions, use which (not that).
• After superlatives and words like “all,” “only,” “every,” use that.

Practice Exercises

Fill in the blanks with that or which (add commas if needed).

1. The movie _____ we saw last night was boring. (Restrictive: many movies, this one was boring.)
2. My sister’s car _____ is ten years old still runs well. (Non-restrictive: she has one car.)
3. This is the only key _____ opens the door. (Use “that” after “only.”)
4. The restaurant _____ serves Italian food is closed today. (Restrictive: many restaurants, only the Italian one.)
5. London _____ is the capital of the UK has many museums. (Non-restrictive: only one London.)

Answers:

1. that (The movie that we saw last night was boring.)
2. , which (My sister’s car, which is ten years old, still runs well.)
3. that (This is the only key that opens the door.)
4. that (The restaurant that serves Italian food is closed today.)
5. , which (London, which is the capital of the UK, has many museums.)

Conclusion

Mastering “that” vs “which” is a small change that makes a big difference in your English writing. Remember: that for essential information without commas, which for extra information with commas. Keep practicing, and soon it will feel natural. For more grammar tips, explore our other guides at EnglishGrammarZone.com!

FAQ

1. Can I use “that” for people?

Yes, you can use “that” for people in informal English, especially in restrictive clauses. Example: The woman that called you is my sister. However, many teachers prefer “who” for people in formal writing. Use which only for things and animals.

2. Is it ever correct to use “which” without a comma?

Yes, but only in British English in some informal contexts. In American English and standard formal writing, “which” requires a comma in non-restrictive clauses. To be safe, always use a comma before which when the clause is non-essential.

3. What about “that” after a preposition?

Never use “that” directly after a preposition. For example, say the house in which I lived or the house that I lived in. The preposition can move to the end of the clause when using that.

4. How do I know if a clause is restrictive or non-restrictive?

Ask yourself: Does the clause narrow down which specific noun I mean? If yes, it is restrictive (use that). If the noun is already clear (e.g., a unique noun like “my mother” or “the sun”), the clause is probably non-restrictive (use which with commas). Also, try reading the sentence without the clause—if the meaning stays the same, use which.