Restrictive clause/non-restrictive clause
>The restrictive clause: the restrictive clause provides essential information
about the subject of the main sentence. It restricts the meaning of a sentence by
identifying the specific qualities of the noun or pronoun.
Example: The man who is walking in front of me is my friend.
Using commas with a restrictive clause is incorrect.
In the last example “who is walking in front of me” identifies who’s the person the subject
is talking about.
>The non-restrictive clause: the non-restrictive clause provides descriptive
Information that isn’t essential to the meaning of the sentence.
Example: The house, which was white and new, was sold.
Commas are used with a non-restrictive clause.