Which vs That: Meaning, Commas, and Style

Quick Answer

Use which, not that, for a nonrestrictive clause about a thing: The final report, which arrived today, is online. The commas show that the clause supplements an already identified report.

In a restrictive clause about a thing, both that and which are grammatical: The report that arrived today and the report which arrived today both identify a particular report. Some house styles prefer that, so check the required style after deciding the meaning.

Do not turn a style preference into a grammar error

The dependable one-way boundary is this: standard edited prose does not use that to introduce a comma-delimited nonrestrictive clause. Restrictive which, however, is established English.

A Four-Case Decision Matrix

Meaning and structure	Available form	Punctuation	Example
Restrictive clause identifying a thing	that or which	No separating commas	The files that/which contain signatures are archived.
Nonrestrictive clause supplementing an identified thing	which, not that	Usually paired commas when embedded	The final file, which contains signatures, is archived.
Fronted preposition before the connector	which, not that	Depends on clause type	The method by which we signed the file is documented.
Comment on a complete preceding clause	which	Normally separated by a comma	The server failed again, which delayed the release.

Cambridge records which in defining and non-defining clauses, while that introduces defining clauses. It also records which for a comment on an entire preceding clause or sentence.

Restrictive Meaning Changes the Referent

Subset:

The reports that arrived before noon were reviewed.

The clause identifies which reports were reviewed. It does not claim that every report arrived before noon.

Already identified set:

The reports, which arrived before noon, were reviewed.

The comma-delimited clause supplements the already identified reports and presents their arrival time as true of that set.

The key question is not whether the shorter sentence The reports were reviewed remains grammatical. It does. Ask whether removing the clause preserves the writer's intended reference and assertion.

Grammar Choice and House-Style Choice Are Different

Sentence	Grammar status	Editorial decision
The contract that expires Friday needs review.	Restrictive and grammatical	Fits styles that prefer that.
The contract which expires Friday needs review.	Restrictive and grammatical	May be changed to that by a specified house style.
The contract, which expires Friday, needs review.	Nonrestrictive and grammatical	Means the contract is already identified.
The contract, that expires Friday, needs review.	Nonstandard in edited prose	Replace that with which.

Merriam-Webster treats both that and which as accepted restrictive connectors and describes the narrower that-only rule as a style position. This page therefore labels a restrictive which edit as style, not correction.

Role, Omission, and Preposition Boundaries

Object connectors may disappear in defining clauses

With connector:

The draft that we approved is final.

Connector omitted:

The draft we approved is final.

The connector is the object of approved. Cambridge permits object-relative omission in a defining clause.

Subject connectors stay

Subject present:

The draft that includes the appendix is final.

Subject missing:

The draft includes the appendix is final.

That is the subject of includes; omitting it breaks the clause structure.

A fronted preposition selects which

Formal placement:

The rule under which we rejected the claim is clear.

Preposition later:

The rule that we rejected the claim under is clear.

A preposition can precede which, but it cannot precede that.

Five Repairs, with the Reason Named

Nonrestrictive connector:

The release, that shipped Friday, contains the fix.

Repair:

The release, which shipped Friday, contains the fix.

The commas mark supplementary information, so use which.

Missing closing comma:

The release, which shipped Friday contains the fix.

Repair:

The release, which shipped Friday, contains the fix.

An embedded nonrestrictive clause needs punctuation at both boundaries.

Repeated object:

The patch which the team tested it is live.

Repair:

The patch which the team tested is live.

Which already supplies the object gap; do not repeat it with it.

Fronted preposition:

The standard to that we referred is public.

Repair:

The standard to which we referred is public.

Use which after a fronted preposition.

Style mislabeled as grammar:

The car which I bought broke down. = incorrect.

Accurate label:

A specified house style may prefer: The car that I bought broke down.

The first sentence uses accepted restrictive which. Change it only when style, cadence, or consistency calls for the edit.

Test Meaning, Structure, and Style

1. The final report, ____ includes the appendix, is online.

2. Without a restrictive-that house rule, which forms can identify files in “the files ____ contain signatures”?

3. The policy under ____ we approved the claim has changed.

4. In “the file that we signed,” may that be omitted?

5. In “the file that contains signatures,” may that be omitted?

Exact Check: Restrictive Which Passed Unflagged

On July 16, 2026, Grammarlyzer returned no issues for the exact restrictive-which sentence below. The alternative with that also returned no issues.

Exact tested seed:

House-style alternative: The car that I bought broke down.

This pair documents two accepted inputs, not a preference or correction. It does not establish behavior for nonrestrictive that, missing commas, fronted prepositions, repeated pronouns, or every publication style.

Frequently Asked Questions

Can which introduce a restrictive clause?

Yes. Both which and that can introduce a restrictive clause about a thing. Some house styles prefer that in this role, so follow the required style guide without labeling restrictive which ungrammatical.

Can that introduce a nonrestrictive clause?

Not in standard edited prose. Use which for a nonrestrictive clause about a thing and set the supplementary clause off with commas, dashes, or parentheses as the sentence requires.

Does removing the clause tell me whether to use which or that?

It is only a first check. Ask whether the clause identifies the intended referent or merely adds information about one already identified. A shortened sentence can remain grammatical while losing the intended reference.

Can I put a preposition before that?

No. Use which after a fronted preposition, as in the process by which we approved the change. With that, leave the preposition later: the process that we approved the change by.

What did Grammarlyzer report for The car which I bought broke down?

On July 16, 2026, the exact sentence returned no issues. The style-preferred alternative with that also returned no issues. This result does not decide the intended meaning or a publication's house style.

What the Direct Sources Support

Cambridge: defining and non-defining relative clauses — reference, punctuation, pronoun, and omission boundaries.
Cambridge: relative pronouns — defining and non-defining which, object omission, and preposition restrictions.
Cambridge: which — thing reference, full-clause reference, and preposition placement.
Cambridge: that — defining relative clauses and the connector's other roles.
Merriam-Webster: that versus which — accepted restrictive use of both forms and the history of the narrower style preference.

These sources do not support calling every restrictive which wrong, treating a deletion shortcut as infallible, claiming that all American style guides enforce one rule, or promising that a checker can infer the writer's intended referent. Those claims have been removed.

A Five-Step Which-or-That Audit

Underline the antecedent. Confirm that the connector refers to a thing or animal; use the dedicated human-reference guidance when the antecedent is a person.
Decide the intended reference. Does the clause identify a subset, or supplement a referent already identified?
Choose punctuation with clause type. Do not separate a restrictive clause; set a nonrestrictive clause off at both boundaries when embedded.
Check the connector's role. Keep subject connectors, omit only eligible defining objects, and use which after a fronted preposition.
Apply the required style last. If a publication reserves that for restrictive clauses, make that consistency edit without mislabeling accepted which as ungrammatical.

What This Page Adds to the Relative-Clause Cluster

The relative clauses guide covers the full system: human and thing antecedents, defining status, connector role, omission, preposition placement, and punctuation. This page isolates the narrower which-versus-that decision and separates grammatical availability from a house-style preference.

The who versus that guide handles human reference, the who versus whom guide handles case, and the comma rules guide handles punctuation beyond relative clauses. Those pages do not replace this pair-specific style boundary.

Decide the Reference Before You Accept an Edit

Use the checker for a second view, then verify clause meaning, punctuation, grammatical role, and required house style yourself.

Try Grammar Checker Free →