which
relative pronoun
adds non-essential detail, usually after a comma
“My car, which is blue, needs new tyres.”
Grammar choices
which vs that
In American usage, that introduces information the sentence needs; which (after a comma) adds extra information you could remove.
that
relative pronoun
introduces essential detail, no comma
“The car that is blue needs new tyres.”
Try it: which word fits?
Drop each word into the blank. The explanation tells you why one works and the other doesn't.
The book ______ I borrowed is overdue.
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Questions about which vs that
What is the difference between which and that?
In American usage, that introduces information the sentence needs; which (after a comma) adds extra information you could remove.
How do I remember which vs that?
Comma, which. No comma, that. If deleting the clause changes the meaning, use that.
Are there exceptions?
British English freely uses "which" for essential clauses too ("the car which is blue"). Most US style guides, including the AP Stylebook and Chicago, prefer that.
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