Only relative pronouns that provide essential information can be omitted. Robin White, whom I met at college, called me last week. Whom is a part of a nonessential clause and cannot be omitted.

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 ...

Qui comes before a verb and relates to the subject of that verb. When used as a relative pronoun, que means ‘who’, ‘whom’, ‘which’ or ‘that’ and is usually used at the start of a ...

Our neighbor's dog, who the mailman was bit by, has been muzzled. The WH-phrase is called a relative pronoun in tranditional grammar. It is an operator--a relative operator. Relative operators are ...