Who

Subject pronoun: who

• Who asked him?
• Who told her?

Object pronoun: whom

• The person (whom) I thought was responsible was not, in fact, to blame.
• Ask not for whom the bell tolls.
• To whom it may concern:

whom has fallen into disuse except when following a preposition.

Interrogative pronoun

An unknown (wh-) person

• Who did you see?
• Hmm... who(m) should we ask?

Relative pronoun

allows further modification of the preceding noun or pronoun.

• Marla's the one who's supposed to be doing this, not me! She's the one who volunteered...
• Look! It's the guy who was at the train station.

Derived forms

who(m)ever: n'importe qui, qui qu'il soit, quiconque, ...

Disambiguation

• Not to be confused with the World Heath Organisation (WHO / OMS)
• or with The Who singing their famous "Who in the world are you" song... ^^

• or with The Hu, for that matter...