Some pronouns have subject forms and object forms.
Pronouns that have subject and object forms are the personal pronouns I, he, she, we, and they.
The subject form is used when the pronoun stands as the subject of a sentence:
I work in a factory.
We go to Mexico every year.
He lives next door to me.
She gives piano lessons.
They are my best friends.
She and I are going to the movies.
Jack and he were late.
The object forms for these pronouns are me, him, her, us, and them.
The object form is used when the pronoun is the object of a verb or of a preposition:
The ball hit him.
We invited them to the party.
Give her the cookie.
The personal pronouns it and you do not have different forms for subject and object.
You must be joking.
Charlie doesn’t believe you.
It is going to fall.
I was too slow to catch it.
The relative pronoun who has the object form whom:
Is that the man who tried to steal the dog?
That’s the man whom I saw yesterday.
Many English speakers have abandoned the use of whom and use who as both subject and object. This use has come to be regarded as acceptable.
An unacceptable and embarrassing error occurs when a speaker uses whom where the subject form is called for. For example, Whom is speaking? Â This error is the result of not having learned the difference between a subject and an object.