|restrictive relative clause|
| Definition -
A clause that helps to precisely identify the sentence's subject.
As opposed to a non-restrictive relative clause, which gives information about the subject that is not necessary for identifying it.
Example - The automobile that is in the tree is mine.
(The restrictive relative clause that is in the tree identifies which car is mine.)
1. Don't place a comma or any other punctuation mark between the subject and the restrictive relative clause.
The automobile, that is in the tree, is mine. (bad)
The automobile that is in the tree is mine. (good)
2. Feel free to use either which or that with restrictive relative clauses. The key thing is to omit the comma.
The automobile which is in the tree is mine.