Prepositions are followed by a noun or pronoun which acts as their object. When the object of a preposition is a pronoun, the pronoun should be in the object form. Examples of object pronouns are: me, him, them, us, her, you etc.
- Can you send this letter to her tomorrow? (NOT Can you send this letter to she tomorrow?)
Here the pronoun her is the object of the preposition to and hence it should be in its objective case.
- She sat among them. (NOT She sat among they.)
- Would you like to come with us? (NOT Would you like to come with we?)
Here the pronoun us is the object of the preposition with.
Who and Whom
These words are often confused. Whom is the objective case of who. When who is used as the object of a preposition, it changes its form to whom.
- Mary saw the men, at least one of whom was wearing a mask, walking through the woods. (NOT Mary saw the men, at least one of who was wearing a helmet…)
Here whom is the object of the preposition of.
Many people don’t know when to use who and whom. Here is a simple tip. Always use whom after a preposition.
- The boys were punished by the teacher.
- By whom were the boys punished? (NOT By who were the boys punished?)
Here whom acts as the object of the preposition by.
If and whether
Both if and whether can be used to introduce an yes / no question.
- I don’t know if she will come. OR I don’t know whether she will come.
After a preposition, only whether is possible.
- A decision about whether betting should be legalized is pending. (NOT A decision about if betting should be …)