|non-restrictive relative clause|
| Definition -
A clause that gives additional, non-identifying information about the sentence's subject.
As opposed to a restrictive relative clause, which gives information that is necessary to precisely identify the sentence's subject.
Example - My car, which is in the tree, has suspension problems.
(We know that the car is my car, so the non-restrictive relative clause which is in the tree is additional, non-identifying information.)
1. Always set off non-restrictive relative clauses with commas.
Barb's husband, who is a real piece of work, is never home.