What’s a restrictive clause, you ask? It’s a clause that narrows down a noun. It can’t be lifted out of the sentence without harming the meaning or specificity of the main clause.

Both Associated Press and Chicago editing styles say that restrictive clauses take “that” and nonrestrictive clauses take “which.” Those “which” clauses are set off with commas.

Lucy Ferriss explains restrictive and nonrestrictive clauses, with help from sisters and supreme beings.

The quasi-grammatical rule, you may recall, is that you use which to introduce a nonrestrictive or nondelining clause, and that to introduce a restrictive or defining clause.

Instead, we’re going to focus on the comma that could have helped make his point clearer. “Seldom has the distinction between a restrictive and a nonrestrictive clause been more important,” wrote Dean ...

A relative clause can be restrictive or nonrestrictive (essential or nonessential) Restrictive relative clauses restrict or define the meaning of a noun and are not set apart by commas.

That it is in the bedroom is additional information) Here is another example of restrictive and nonrestrictive clauses with ‘who’: My brother who is a dermatologist is in the US.

It is true that British writers use which for both restrictive and nonrestrictive clauses, as linguists point out. It is also true that the distinction American grammarians observe is essentially ...