Which vs That in English Grammar | Rules, Differences & Examples

What Is the Function of “Which” and “That”?

Both which and that are relative pronouns. They introduce relative clauses, which give more information about a noun.

Example:

• The book that you gave me is interesting.
• The book, which you gave me, is interesting.
• But the meaning and punctuation are different.

The Core Difference: Restrictive vs. Non-Restrictive Clauses

This is the most important concept. Let’s explain one by one.

A. “That” → Restrictive (Essential Information)

Use that when the information is necessary to identify the noun.

Without the clause, the sentence meaning changes.

• Example: The students that studied hard passed the exam.
• Meaning: Only the students who studied hard passed.

If you remove the clause: The students passed the exam. (Meaning changes completely.) So the clause is essential.

No commas are used with “that.”

B. “Which” → Non-Restrictive (Extra Information)

Use which when the information is extra and not essential.

The sentence meaning stays clear even if you remove the clause.

• Example: The students, which studied hard, passed the exam. (Incorrect structure)
• Correct example: My car, which is very old, still runs perfectly.

If we remove the clause: My car still runs perfectly. The sentence still makes sense. Commas are required with “which” in this case.

Punctuation Rule

This is where most students make mistakes.

• ‘That’ is used in restrictive clause and require no commas
• ‘Which’ is used in non-restrictive clause and require commas

Comparison:

The house that is painted blue is mine. (Only the blue house)

The house, which is painted blue, is mine. (We already know which house. Blue is extra info.)

Meaning Difference (Very Important)

Let’s compare two similar sentences:

• Sentence 1: The cakes that have chocolate are delicious.

Meaning: Only chocolate cakes are delicious.

• Sentence 2: The cakes, which have chocolate, are delicious.

Meaning: All the cakes have chocolate, and they are delicious.

When “That” Is Preferred

In modern American English, “that” is preferred in restrictive clauses.

Especially:

• After superlatives
• After words like all, everything, something
• After ordinal numbers

Examples:

• She is the best teacher that I have ever met.
• Everything that he said was true.
• This is the first book that I bought.
• Using “which” in these cases sounds unnatural.

When “Which” Is Required

“Which” must be used:

1. After a preposition

• The house in which I live is old. (Not: The house in that I live)

2. In non-restrictive clauses

• My laptop, which I bought last year, is already slow.

3. Referring to an entire sentence

• He failed the exam, which surprised everyone. Here “which” refers to the whole situation.

Common Mistakes Students Make When Using That vs Which

Mistake 1: Using comma with “that”

• The book, that I bought, is new. (Wrong)
• Correct: The book that I bought is new.

Mistake 2: Using “which” without comma (non-restrictive meaning)

• My car which is red is fast. (Confusing)
• Correct: My car, which is red, is fast. OR, The car that is red is fast.

Mistake 3: Using “that” after preposition

• The office in that he works is small. (wrong)
• Correct: The office in which he works is small.

Can “Which” Be Used in Restrictive Clauses?

Yes — but mainly in British English.

In American English:

• Restrictive → “that” preferred
• Non-restrictive → “which”

So for clarity and exams, students should follow:

• Use “that” for essential clauses
• Use “which” for extra information

Advanced Concept: Removing the Relative Pronoun

In restrictive clauses, “that” can sometimes be removed.

Example:

• The book that I bought is expensive.
• The book I bought is expensive.

But “which” in non-restrictive clauses cannot be removed.

• My car, which is red, is fast. (Removing “which” breaks structure.)

Exam Tip for Students on Which vs That

If the clause: Is necessary → use that

Is extra information → use which with commas

Simple trick:

• No comma → THAT
• Comma → WHICH

Practice Sentences on Which vs That

Choose the correct word:

1. The movie ___ we watched was boring.
2. My brother, ___ lives in Lahore, is a doctor.
3. This is the best phone ___ I have used.
4. The office in ___ she works is large.

(Answers: 1. that 2. which 3. that 4. which)

Final Conclusion

The confusion between which vs. that mainly comes from misunderstanding clause types.

Remember:

• “That” = essential information
• “Which” = extra information