📖 Relative Clauses Rules: Who, Which, That, Whose, Whom

• who → people (subject/object)
• whom → people (object, formal)
• which → things, animals
• that → people or things (defining clauses only)
• whose → possession (people or things)

Defining: No commas, essential information, can use "that".
Non-Defining: Commas, extra information, cannot use "that".
Example: "My brother who lives in London is a doctor." (defining - I have more than one brother)
"My brother, who lives in London, is a doctor." (non-defining - I have only one brother)

In defining clauses, when the pronoun is the object, you can omit it.
• The book (that) I read was good.
• The woman (who) you met is my aunt.