Answer First
✅ Standard With Commas
Which is standard for nonrestrictive clauses (the extra info kind). Commas required.
❌ Common Misbelief
“Which is always wrong without a comma” is too absolute. The meaning and comma are the real signal.Source-1✅
Think of which vs that as a clause-type question first, and a word-choice question second.
The which vs that debate usually feels like a grammar rule, but it’s really about information. One clause is needed to identify the noun. The other is bonus detail. The commas tell you which one you’re dealing with.
Table of Contents
Correct Form
Both which and that can be correct. What changes is the type of relative clause and the punctuation.
- Restrictive (also called essential): the clause defines which noun you mean. Commas do not belong here.
- Nonrestrictive (also called nonessential): the clause adds extra detail. Commas wrap the clause, and that is not used as the relative pronoun in this pattern.Source-2✅
Two Sentences, Two Meanings
✅ Restrictive The file that sits in the folder is the one to review.
Meaning: there are multiple files; the clause selects one.
✅ Nonrestrictive The file, which sits in the folder, is the one to review.
Meaning: there is a clearly identified file already; the clause is extra detail.
| Pattern | Typical Signal | What The Clause Feels Like | Example |
|---|---|---|---|
| No commas | Restrictive | Needed to identify | The notes that mention the timeline are updated. |
| Commas | Nonrestrictive | Extra detail | The notes, which mention the timeline, are updated. |
The comma choice is not cosmetic. It can change the scope of the noun and the logic of the sentence.Source-3✅
Why The Mistake Happens
The mix-up is common because the sentence often still “sounds fine” either way. The tricky part is that sound doesn’t show commas.
- House styles vary: many prefer that for restrictive clauses, but the broader grammar system allows which in restrictive contexts in some writing.
- Writers often learn a single headline rule, then apply it to every sentence, even when the clause is clearly nonessential.
- Relative clauses can be subtle: the difference is sometimes about what the writer assumes is already identified in context.Source-4✅
Common Pattern: drafts often treat commas as “optional.” In edited writing, commas around a nonrestrictive clause are part of the meaning, not decoration.
Pronunciation
In speech, the difference between which and that is usually about rhythm, not a visible comma. A speaker might add a slight pause for nonessential information, but it isn’t always consistent.
Word Parts
Which and that aren’t just “choices.” They play different grammatical roles across English, so the right pick depends on what the clause is doing.
- Which as a relative pronoun
- Introduces a clause about a thing (and often marks nonessential information when set off by commas).
- That as a relative pronoun
- Often used in restrictive clauses; it does not pair with commas in the nonrestrictive pattern.
- That beyond relative clauses
- Also shows up as a demonstrative (“that device”) and as a clause-linker (“I noticed that the file changed”).
One more real-world detail: in some restrictive clauses, the relative pronoun can be omitted when it’s the object (“the report I saved”). This affects flow, but not the restrictive/nonrestrictive distinction.Source-6✅
Related Forms
The “family” around these words matters because it explains why which feels natural in some sentences and that feels natural in others. Same neighborhood, different jobs.
Which Family
- which (relative / interrogative)
- whichever (choice among options)
- which one (question phrasing)
That Family
- that (relative / demonstrative)
- this and these (near reference)
- those (far/plural reference)
Worth Noticing: that can introduce a full content clause (“I noticed that the light changed”). Which does not fill that same slot, so swapping them can create a different structure, not just a different style.
Common Misspellings Table
This isn’t really about spelling. It’s about the most common mix-ups people make with which, that, and commas.
| Status | Pattern | What Goes Wrong | Clean Example |
|---|---|---|---|
| ❌ | Nonrestrictive idea, but no commas | The clause reads as essential even when it’s meant as extra. | The manual, which is updated monthly, is online. |
| ❌ | that wrapped in commas | It suggests a nonrestrictive structure that doesn’t fit the standard pattern. | The manual that is updated monthly is online. |
| ✅ | Restrictive meaning, that, no commas | Matches the essential function. | The update that fixes the bug is installed. |
| ✅ | Nonrestrictive meaning, which, commas | Keeps the clause as extra detail. | The update, which fixes the bug, is installed. |
What Most Readers Expect In Edited Text
- That tends to read as defining information.
- Which plus commas tends to read as parenthetical information.
- The comma set is a meaning marker, not a decoration.
FAQ
Sıkça Sorulan Sorular
Is “That” Always Wrong With Commas?
In the standard nonrestrictive relative-clause pattern, that is not the usual relative pronoun. Commas typically pair with which for extra information.
Can “Which” Be Restrictive Without A Comma?
Some writing uses which in restrictive clauses. Many editors still prefer that in that slot, so the “correct” choice can depend on the editing standard.
What’s The Biggest Meaning Trap In Which Vs. That?
The commas. They decide whether the clause reads as essential or extra.
Is “Which” Only For Things?
Which commonly refers to things in relative clauses. It also appears in questions (“which option?”) and can refer to an entire idea in a nonrestrictive clause.
Does “That” Have Uses Beyond Relative Clauses?
Yes. That works as a demonstrative (“that device”) and as a clause-linker (“I noticed that the device changed”). Those uses are different structures from relative clauses.