Who and whom sometimes cause problems.
Some people think that whom is going to disappear from
the English language, to be replaced in all cases by who.
However, careful speakers do make the distinction between who
and whom. Here are some basic distinctions between
who and whom.
Who is used as the subject of a verb.
(As an interrogative pronoun):
Who’s calling, please?
(As a relative pronoun):
The man who called asked to speak to my father.
(In this sentence, the relative pronoun that can
also be used.)
(As the subject of a noun clause):
I wonder who is going to win the election.
Whom is used in more formal speech and writing as
the object of a verb or preposition. Informally, whom
is often replaced with who.
In the next, less formal, sentences where whom is
an interrogative pronoun, whom or who
can be used:
Did you tell anybody about this? Whom did you tell?
Did you tell anybody about this? Who did you tell?
Whom are you going to meet?
Who are you going to meet?
In the next group of sentences, whom is a relative
pronoun. Here it’s possible to replace whom with
who or that, or to omit the relative
pronoun entirely:
She married the man whom she really loved, and lived
happily ever after.
She married the man who she really loved, and lived
happily ever after.
She married the man that she really loved, and lived
happily ever after.
She married the man Ø she really loved, and
lived happily ever after.
In the next three sentences, whom appears directly
after a preposition. Here only whom is possible, and
the pronoun can’t be omitted.
To whom should I address the letter?
The person with whom you should speak is the vice-consul
in charge of community relations.
In some other sentence constructions, the choice of who
or whom may be more problematic.