When to Use That vs Which (With Examples)

When to Use That vs Which (With Examples)

Quick answer: Use "that" for essential (restrictive) clauses with no commas, and "which" for nonessential (nonrestrictive) clauses set off by commas.

Definition of "That"

"That" is a demonstrative pronoun and conjunction used to introduce restrictive (essential) relative clauses. Its job is to tighten a sentence so the clause is necessary to identify the noun.

Etymology: "That" comes from Old English þæt, originally a neuter demonstrative pronoun meaning "the one" or "the thing that."

Definition of "Which"

"Which" is a relative pronoun used mostly to introduce nonrestrictive (nonessential) clauses that add extra information and are usually separated by commas.

Etymology: "Which" traces back to Old English hwilc (from hwelc), meaning "what kind" or "which one."

Key Differences

Example Sentences

Examples Using "That"

• The book that has the red cover is mine. (You must know which book.)
• She ate the sandwich that I made this morning. (Which sandwich is defined.)
• Cars that run on electricity are becoming more common. (Defines the subset of cars.)
• He’s the scientist that discovered the new compound. (Essential detail identifying which scientist.)

Examples Using "Which"

• My laptop, which I bought last year, needs a new battery. (Extra info; removeable.)
• The concert, which started late, still ended on time. (Parenthetical detail.)
• We painted the kitchen, which brightened the entire house. (Nonessential comment about the effect.)
• The museum, which has free admission on Sundays, draws large crowds. (Additional info set off by commas.)

Memory Trick

Use this simple mnemonic: "No comma — use THAT. Comma — use WHICH." Imagine "that" as a tight, no-frills connector that doesn't need the extra space commas provide. "Which" likes breathing room — it wants commas.

Another quick line: "That Tightens; Which Adds." Say it out loud before you write the clause to decide which fits.

Quick Quiz

Fill in each blank with "that" or "which." Answers are shown immediately after the questions so you can check yourself.

1. The painting ___ hangs in the lobby is by a local artist.
   Answer: that
2. The painting, ___ was restored last year, now looks brand new.
   Answer: which
3. Choose the software ___ supports batch processing.
   Answer: that
4. Our new printer, ___ I love for its speed, saves a lot of time.
   Answer: which

Practical Tips You Can Apply Now

• Scan your sentence: If the clause is needed to identify the noun, pick "that" and skip commas.
• Try removing the clause. If the sentence still makes sense and keeps the same person/thing, use "which" with commas.
• For formal American English, stick closely to this rule. In British English, "which" sometimes appears in restrictive clauses — but clarity is king.
• If you rewrite and still feel unsure, run your sentences through a grammar tool or an AI writer. For fast rewrites and paraphrasing, try Rephrasely's AI writer or paraphraser at Rephrasely.

Want to test whether your text uses AI-generated phrasing or to check originality? Use Rephrasely’s AI detector and plagiarism checker to be safe. You can also use the composer to build example sentences automatically.

Frequently Asked Questions

Can I use "which" without commas in restrictive clauses?

In American English, you should avoid using "which" for restrictive clauses—use "that" instead. British English sometimes allows restrictive "which," but for clarity and consistency, follow the comma rule: commas → which; no commas → that.

Do the rules change for people?

For people, prefer "who" or "whom" (e.g., "the person who called"). "That" can sometimes be used for people in informal contexts, but "who" is clearer and more polite in formal writing.

What if I accidentally use the wrong one—will meaning change?

Yes. Using "which" with commas may make the clause nonessential and change whether the noun is identified. If precision matters (legal text, instructions, technical writing), choose carefully to avoid ambiguity.