Short answer
In edited US prose, ‘that’ is often preferred for restrictive clauses that identify which thing is meant, while ‘which’ is standard for nonrestrictive clauses that add extra information. Restrictive ‘which’ is also established English, although some style guides prefer the narrower division. Commas and the clause’s role matter more than a blanket ban. 1 2 3
Both are relative pronouns, but US editorial convention favors “that” for restrictive clauses and “which” for nonrestrictive, though actual usage is more flexible.
On this page
At a glance
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| Question | which | that |
|---|---|---|
| Common in restrictive clauses? | Yes, but sometimes debated | Yes, preferred in edited prose |
| Common in nonrestrictive clauses? | Yes, standard | Rare, generally avoided |
The table summarizes the stated definitions and scope. 1 2 3
What each thing is
Which. In edited US English, “which” is a relative pronoun commonly used to introduce nonrestrictive clauses, though it can also introduce restrictive clauses, especially when stylistic preferences allow. Its use in restrictive clauses is sometimes debated. 1 2
That. In edited US English, “that” is a relative pronoun most often used to introduce restrictive clauses, specifying essential information about a noun. Its use in nonrestrictive clauses is now rare and generally avoided in modern prose. 1 3
Key differences
The main distinction is the type of relative clause: “that” is preferred for restrictive clauses, while “which” is standard for nonrestrictive clauses in US-edited writing. This is a stylistic tendency, not an absolute rule. 1 2 3
How to tell them apart
A practical test: if the clause is essential to the noun’s meaning, use “that”; if it adds extra, nonessential information (often set off by commas), use “which.” However, “which” is also found in restrictive clauses, especially outside strict editorial contexts. 1 2
Where they overlap
Both words can introduce restrictive clauses, and many reputable writers use “which” in this way. The overlap is real, though some editors prefer to reserve “which” for nonrestrictive clauses for clarity. 1 2 3
Edge cases
While “that” was once used for nonrestrictive clauses, this is now rare in modern prose. Poetic or historical texts may still show “that” in nonrestrictive roles, but such usage is not standard in current edited US English. 1 3
Why the distinction exists
The distinction is mainly editorial, arising from efforts to clarify sentence structure. Historically, both words were used interchangeably, but style guides later encouraged separating their functions for consistency and readability. 1
Common misconceptions
A common misconception is that using “which” in restrictive clauses is always wrong. In reality, this usage is common and accepted in edited US English, though some style guides recommend “that” for consistency. 1 2
Examples
Consider: “The car that is parked outside is mine” (restrictive) versus “The car, which is parked outside, is mine” (nonrestrictive). The first specifies which car; the second adds extra information. Both are correct in context. 1 2 3
Sources
Sources checked October 3, 2026.
- Merriam-Webster — Which vs. That: Correct Usage. Usage guide: definitions, examples and exceptions.
- Merriam-Webster — Which Definition & Meaning. Dictionary entry: definitions, usage examples and word history.
- Merriam-Webster — That Definition & Meaning. Dictionary entry: definitions, usage examples and word history.