A relative clause can be introduced by either a relative pronoun or a relative adverb. A relative clause can be restrictive or nonrestrictive (essential or nonessential) Restrictive relative clauses ...

They are introduced by a relative pronoun like 'that', 'which', 'who', 'whose', 'where' and 'when'. For example: I won’t stand by the man who smells of slime. In this example, the relative ...