To understand how to use ‘who’, ‘whom’ and ‘whose’ you first have to understand the difference between subjects, objects and possessives.
The subject does the action:
- He likes football.
- She goes to university.
- They enjoy travelling.
The object receives the action:
- The employees respect him.
- I know her.
- The sailors waved to us.
Possessives tell us the person something belongs to:
- His car is new.
- I like his latest novel.
- We returned to our hotel.
1. 'Who' is a subject pronoun like 'he', 'she' and 'they'. We use 'who' to ask which person did an action or which person is in a certain state.
- Who made the birthday cake?
- Who is in the bathroom?
- Who is going to the market this afternoon?
2. 'Whom' is an object pronoun like 'him', 'her' and 'us'. We use ‘whom’ to ask which person received an action.
- Whom are going to ask to Mary’s party this evening?
- Whom did they choose as a team leader?
- Whom did he blame for the accident?
3. “Whose” is a possessive pronoun like 'his', and 'our'. We use 'whose' to find out which person something belongs to.
- Whose bag is this?
- Whose cell phone keeps ringing?
- Whose dog is barking outside?