English — Prepositions in relative clauses
When a relative clause contains a preposition, English lets you place it in two positions. Informally the preposition stays at the end: the man who I spoke to. Formally it moves to the front, before whom or which: the man to whom I spoke. Both are correct; the choice signals register.
How it works
In everyday English the preposition stands at the end and the relative pronoun is who, that, or dropped: the film that we talked about / the film we talked about. In formal English the preposition is fronted and must be followed by whom (for people) or which (for things): the film about which we talked. A fronted preposition cannot combine with who, that, or a zero pronoun — about who and about that are impossible.
Examples
| Informal (end position) | Formal (fronted preposition) |
|---|---|
| the man who I spoke to | the man to whom I spoke |
| the woman that I work with | the woman with whom I work |
| the topic we talked about | the topic about which we talked |
| the house I grew up in | the house in which I grew up |
| the reason he came for | the reason for which he came |
| the friends I rely on | the friends on whom I rely |
| the tool it was made with | the tool with which it was made |
Good to know
The old rule that you must never end a sentence with a preposition is a myth; the end position is standard and natural. Reserve the fronted preposition + whom/which for formal writing, and use it only with a one-word preposition. Phrasal verbs keep their particle at the end: the results we're looking forward to, never to which we are looking forward. Also note whom, not who, after a fronted preposition: to whom I spoke, not to who I spoke.