Subject vs Object Relative Pronouns

In relative clauses, the pronoun can function as the subject or the object, and this determines whether you can omit it. A subject pronoun performs the action: "The woman who lives next door" — "who" is the subject (she lives). An object pronoun receives the action: "The woman who I met at the party" — "who" is the object (I met her). The crucial difference: object pronouns can be omitted — "The woman I met" — but subject pronouns cannot.

To decide whether a pronoun is the subject or the object, look at the word after it. If a verb follows immediately ("who lives"), the pronoun is the subject. If another subject follows ("who I met"), the pronoun is the object and can be dropped. This omission is extremely common in spoken English: "The book I read" (not "The book which I read") sounds more natural to most native speakers. Cambridge B2 exams frequently test this by asking which sentences are correct with and without the pronoun, so understanding the subject-object distinction is essential for exam success.