A relative clause acts as a clause that modifies a noun or pronoun .
Relative clauses can either be restrictive or nonrestrictive .
A restrictive relative clause is essential in order to complete the meaning of the main clause. That's the one which I like best. A nonrestrictive relative clause adds definition to the main clause, but is not necessary for meaning. Nonrestrictive relative clauses are set off by commas. The orange car, which is my favorite , has seating for six.