relative pronouns

The most common relative pronouns are who/whom, whoever/whomever, whose, that, and which. (Please note that in certain situations, "what," "when," and "where" can function as relative pronouns.) Relative pronouns introduce relative clauses, which are a type of dependent clause. Relative clauses modify a word, phrase, or idea in the main clause. The word, phrase, or idea modified is called the antecedent. In the following examples, that and whom modify the subject:

The house that Jack built is large.

The professor, whom I respect, recently received tenure.
The type of clause determines what kind of relative pronoun to use. Generally, there are two types of relative clauses: restrictive (defining) clause and non-restrictive (non-defining) clause. In both types of clauses, the relative pronoun can function as a subject, an object, or a possessive pronoun ("whose").

Relative Pronouns in Restrictive Relative Clauses

Relative pronouns that introduce a restrictive relative clause ARE NOT separated from the main clause by a comma. Restrictive relative clauses (also known as defining relative clauses) add essential information about the antecedent in the main clause. The information is crucial for understanding the sentence's meaning correctly and cannot be omitted. In other words, without the restrictive relative clause, the sentence does not make sense.