請問 who 同 whom 的分別及用法

who is a subjective pronoun (subject of the side clause), and whom is the corresponding dative pronoun (an object of the side clause).

Who represents A PERSON who is doing something.
WHOM represents A PERSON something is done to.

A easy way to tell:
WHO refers to I, He, She or They
WHOM refers to Me, Him, Her or Them.
Subsitute it in a sentence and you can tell if it is accurate.

He gives the pen to him.
Who gives the pen to whom?

She ate the apple.
Who ate the apple?

This book belongs to me.
THis book belongs to whom? (or more correctly, Whom does this book belong to?)

To (whom/who) have you talked to about this matter?
-- You talked to ?? -
Put in I for ?? you talked to I is not correct grammer
Put in ME: you talked to me is correct.
So the correct usage is
To WHOM have you talked to about this matter.

The most important thing is find out who is the main character; in the sentence. In the above sentence, YOU is main character who do the action of talking.

Another easy way to tell is, WHOM (or him, me, her, them) usually comes after a preposition.
Please give this to him. Whom do you give this to?
Betty go shopping with her. Whom does Betty go shopping with?
I buy this sandwich for him. Whom do I buy the sandwich for?
I think of him a lot. Whom do I think of?

Please note that nowaday in common, informal every day use, sometimes sentences like Who do you go out with, Who did you talk to, are acceptable.

whom 係 indirect speech
eg. To whom did Mary give her pen ?
who 係 direct speech
eg.Who did Mary give her pen to?

who 同whom 最大既分別係單雙數既問題
如果你問個一堆係咩人 就用whom
如果係問個一個係咩人 就用who
e.g Whom are the members of Math Club?
e.g Who is your best friend?