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Relative clauses with prepositions: in which, whereby
C1 C1 grammar · lesson 15 of 16
You already know defining and non-defining relative clauses. At C1 you can use prepositions before which and whom, plus formal words like whereby, to write precise, academic sentences.
Preposition + which / whom
In everyday English, a preposition usually goes at the end of a relative clause. In formal English, it moves to the front, before which (things) or whom (people).
| Informal | Formal |
|---|---|
| the house (that) I grew up in | the house in which I grew up |
| the person (who) I spoke to | the person to whom I spoke |
| the topic (that) we talked about | the topic about which we talked |
With phrasal verbs, the preposition (particle) usually stays with the verb: the problem which we looked into, not into which we looked.
Whereby, in which case, at which point
- whereby = “by which / through which”. Used for systems, methods and agreements.
- in which case = “and if that happens”.
- at which point = “and at that moment”.
The school has a system whereby older students help younger ones.
The train may be late, in which case we’ll take a taxi.
The speaker made a joke, at which point everyone relaxed.
Quantifier + of which / of whom
In non-defining clauses, we can use some / many / all / none / both / most / neither + of which / of whom.
She has three brothers, all of whom live abroad.
We tested ten products, none of which were perfect.
The museum has many paintings, most of which are from Italy.
This is the reason for which the event was cancelled.
Anna, to whom I owe a great deal, was my first teacher.
It was a period during which many new ideas appeared.
Omar bought a new phone, the screen of which broke within a week.
Common mistakes
✗ The woman to who I wrote never replied.
✓ The woman to whom I wrote never replied.
✗ The town in that I was born is small.
✓ The town in which I was born is small.
✗ I have two cousins, both of them are doctors.
✓ I have two cousins, both of whom are doctors.
✗ The room in which we stayed in was noisy.
✓ The room in which we stayed was noisy.