Relative clauses begin with a relative pronoun, although in conversation and in a great deal of writing the relative pronoun is left out. The relative pronoun represents the noun that the relative clause is modifying. In other words, “who” in the example above represents and replaces “students” in the relative clause. The following are relative pronouns: who, whom, whose, that and which. The chart below shows when to use each relative pronoun.
- WHO When the head noun is human and is the subject of the sentence.
Note: “Who” is often used in object position by native speakers of English, even though “whom” is the correct pronoun to use there. “The lady who lives next door sells is a good gardener.”
- WHOM When the head noun is human and is the object of the sentence. However, most Americans ignore this rule, and only use “who.” “I saw the man whom you lent your car to.” “I saw the man to whom you lent your car.”
- WHICH In some writing and formal speech when the head noun is not human. “The study which he refers to is outdated.” “The study to which he refers is outdated.”
- THAT In writing and especially in conversation when the head noun is either human or nonhuman. “That” is much more common than “which.” “The study that he refers to is outdated.” (You cannot say “The study to that he refers is outdated.)
- WHOSE “Whose” is a possessive relative pronoun that can refer to either a human or nonhuman head noun. “The salesman whose sales are the largest will earn a bonus.” “I bought a book whose cover is made of leather.”