The choice between who and whom (or whoever and whomever) occurs primarily in subordinate clauses and in questions. Who and whoever, subjective-case pronouns, are used for subjects and subject complements. Whom and whomever, objective-case pronouns, are used for objects.

An exception to this general rule occurs when the pronoun functions as the subject of an infinitive (see the section on subjects or objects of infinitives below).

Consult the chart below for a summary of the trouble spots with who and whom.

In subordinate clauses

When who and whom (or whoever and whomever) introduce subordinate clauses, their case is determined by their function within the clause they introduce.

In the following two examples, the pronouns who and whoever function as the subjects of the clauses they introduce.

The subordinate clause is who earns the most points. The verb of the clause is earns, and its subject is who.

The writer selected the pronoun whomever, thinking that it was the object of the preposition by. However, the object of the preposition is the entire subordinate clause whoever is interested in the effects of racial prejudice on children. The verb of the clause is is, and the subject of the verb is whoever.

When functioning as an object in a subordinate clause, whom (or whomever) also appears out of order, before the subject and verb. To choose the correct pronoun, you can mentally restructure the clause.

The subordinate clause is whom you will meet later. The subject of the clause is you, and the verb is will meet. Whom is the direct object of the verb. The correct choice becomes clear if you mentally restructure the clause: you will meet whom.

When functioning as the object of a preposition in a subordinate clause, whom is often separated from its preposition.

Whom is the object of the preposition to. In this sentence, the writer might choose to drop whom: The tutor I was assigned to was very supportive.

note: Inserted expressions such as they know, I think, and she says should be ignored in determining whether to use who or whom.

Who is the subject of was suffering, not the object of knew.

In questions

When who and whom (or whoever and whomever) are used to open questions, their case is determined by their function within the question.

Who is the subject of the verb was.

When whom functions as the object of a verb or the object of a preposition in a question, it appears out of normal order. To choose the correct pronoun, mentally restructure the question.

Whom is the direct object of the verb did nominate. This becomes clear if you restructure the question: The Democratic Party did nominate whom in 1952?

For subjects or objects of infinitives

An infinitive is the word to followed by the base form of a verb. (See B3-b.) Subjects of infinitives are an exception to the rule that subjects must be in the subjective case. The subject of an infinitive must be in the objective case. Objects of infinitives also are in the objective case.

The infinitive phrase whom to believe is the direct object of the verb know, and whom is the subject of the infinitive to believe.