How does one correctly apply “in which”, “of which”, “at which”, “to which”, etc.?

I'm confused with which one to apply when constructing sentences around these.


The trick to knowing how to use; of which, at which, in which, to which, from which is to analyse the prepositional phrases, phrasal verbs, verbs and prepositions:

  1. He /spoke of/ war and peace and many other topics that day.
    The topic /of which he spoke/ was complex.
    The verb here that means to speak about a topic is /to speak/ of a topic/: to mention

  2. The party /at which/ he spoke/ was noisy.
    Phrase: A party is held /at a place/. It is implied.
  3. The situation /in which/ we found ourselves was dire.
    Phrase: /to find oneself /in a situation.
  4. The bonds /from which/ we broke free were tight.
    phrase: to /break free/ from bonds.
  5. The town /to which/we were driving was 50 ks away.
    phrase: to /drive/ to a place.

Summary (and not a complete answer but a general one): The preposition depends on the verb that takes a preposition, a phrasal verb that includes a preposition, or it depends on the prepositional phrase used. Also, there are many other prepositions that can be paired with which: under, during, about, over, etc.

  • What's the difference between "The topic he spoke were complex." vs "The topic /of which he spoke/ were complex"? – Pacerier Feb 7 '17 at 11:14
  • And also "The town which we were driving to was 50 ks away" vs "The town /to which/we were driving was 50 ks away". – Pacerier Feb 7 '17 at 11:17
  • @Pacerier /The topic he spoke/ is not grammatical/idiomatic. To speak ON or OF or ABOUT a topic. All with different meanings. In the second sentence the only difference is informality/spoken English versus more formal/written English – Lambie Feb 7 '17 at 13:36
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    @Mr. Hyde One can sometimes shift the preposition in writing or in speech, yes: "the party which he spoke at was" etc.. Bear in mind, though, that in non-literary writing, the preposition would not be shifted. Which without in is not part of this question. The point here is about the prepositioins. – Lambie Mar 17 '18 at 13:31
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    @deadManN Yes, that's fine and it is a completely different question, in fact. My answer is about which preposition to use, not where to place it.... – Lambie May 14 '20 at 20:50

Probably easiest to explain through examples. Each phrase simply means "the thing that we've already mentioned", e.g.

  • The box in which the books are kept

  • The town of which we were speaking

  • The time at which we will arrive

  • The destination to which we were heading

I'm sure there's a grammatically-correct term, but they're really just the correct forms of "the box the books are kept in"/"the town we were speaking of", i.e. removing the trailing preposition.

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    I've seen them called a 'complex relative phrase', in contrast to a 'simple relative phrase' which consists of a relative word on its own (e.g. "which", "who", "why" etc.) – BillJ May 1 '16 at 17:30
  • The point is to know which preposition to use: in, of, about, in, under, over, etc. You are not answering the question. speak of a matter, of which; fall under a statute, under which, arrive at a time, at which. And so forth. – Lambie Nov 17 '18 at 13:45

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