Classic Errors and Helpful Hints

Strictly speaking, it is correct to use who as the subject of a verb and whom as the object, e.g. 'Who saw you?' but 'Whom did you see?' It is also strictly right to use whom after a preposition, as in 'To whom were you talking just now?' In practice, few people follow this rule; most use who all the time, and a sentence like 'To whom were you talking?' can sound too formal.