Prepositions might seem small, but they carry big meaning. In English, words like in, on, at, and of guide how ideas connect in time, space, or logic.
When paired with “which,” these prepositions form powerful expressions used in writing, conversation, and formal communication.
If you’ve ever hesitated between “in which” and “at which” or wondered when to use “of which”, this guide will clear it all up — with examples, real-world use, and memorable tips.
Why Prepositional ‘Which’ Phrases Matter
You use prepositional phrases with which when you want precision. They connect ideas smoothly and make your writing sound more natural and intelligent.
Take this example:
“The meeting at which the plan was approved took place last Monday.”
Here, “at which” shows where or when the approval happened. Removing it changes the rhythm and clarity of the sentence.
Without these prepositions, English sentences can lose depth, context, or correctness — especially in formal writing.
Understanding the Function of Prepositions
Prepositions are connecting words. They link nouns, pronouns, or phrases to other parts of a sentence. Think of them as linguistic glue.
Main purposes of prepositions:
- Time: at 5 p.m., in 2025, on Monday
- Place: in the room, at the park, on the wall
- Direction: to the store, into the forest, toward success
- Manner or means: by car, through practice, with confidence
When combined with “which,” prepositions help describe relationships more precisely — especially in formal or written contexts.
Identifying Contexts That Determine the Right Preposition
The right preposition depends on what kind of relationship you want to show. English uses context-driven logic.
Time
Use when describing moments, durations, or sequences.
Example:
- “The year in which he graduated was 2020.”
- “The ceremony at which they announced the results lasted two hours.”
Place
Used for describing position or setting.
Example:
- “The city in which she was born is beautiful.”
- “The corner at which two roads meet.”
Reason or Cause
Shows purpose or motivation.
Example:
- “The reason for which they gathered was unity.”
Means or Manner
Explains how something happened.
Example:
- “The channel through which the water flows is ancient.”
Possession or Relationship
Shows belonging or association.
Example:
- “The project, the details of which remain secret, began last year.”
Using ‘Which’ with Common Prepositions
‘In Which’
Meaning: Refers to a place, time, or situation.
Examples:
- “The country in which he lives is peaceful.”
- “The year in which they met changed everything.”
Tip: You can often replace “in which” with “where” or “when” in casual writing.
Comparison:
| Formal | Informal |
|---|---|
| The house in which I grew up. | The house where I grew up. |
‘On Which’
Meaning: Refers to surfaces, days, or topics.
Examples:
- “The table on which the book rests is antique.”
- “The day on which we met remains special.”
Note: It’s also used for abstract ideas:
“The principle on which our company operates is trust.”
‘At Which’
Meaning: Specifies an exact point in time, place, or event.
Examples:
- “The moment at which she realized the truth was unforgettable.”
- “The concert at which they performed drew thousands.”
Quick Tip:
Use “at” when you can pinpoint something — like an event, time, or place.
| Situation | Example |
|---|---|
| Specific time | “The instant at which it broke.” |
| Event | “The meeting at which we agreed.” |
| Place (small point) | “The junction at which two roads cross.” |
‘Of Which’
Meaning: Expresses possession, relationship, or belonging — often replacing “whose.”
Examples:
- “The company, of which he is the founder, started in 2010.”
- “The book, the cover of which was torn, is rare.”
When to use:
- In formal writing or academic tone.
- When referring to things, not people.
Can you use ‘whose’?
Yes, but only if it doesn’t sound awkward.
“The car, whose engine failed, was new.”
“The car, of which the engine failed, was new.” (formal)
‘For Which’
Used to show reason, purpose, or cause.
Example: “The cause for which they fought was freedom.”
‘Through Which’
Used for processes, channels, or pathways.
Example: “The pipe through which water flows is rusted.”
‘By Which’
Used for means or methods.
Example: “The method by which results were calculated was transparent.”
‘From Which’
Used for source or origin.
Example: “The town from which she came is near the coast.”
‘Under Which’ and ‘Over Which’
Used for physical or figurative coverage or position.
Examples:
- “The bridge under which they stood.”
- “The rule over which they argued.”
Syntax and Style: Combining Prepositions with ‘Which’
In English, prepositions can appear before or after “which,” depending on tone and formality.
| Structure | Example | Register |
|---|---|---|
| Preposition before “which” | “The house in which he lives.” | Formal |
| Preposition at end | “The house he lives in.” | Informal |
Rule of Thumb:
- Use fronted prepositions (“in which”) in formal writing (essays, reports).
- Use stranded prepositions (“he lives in”) in spoken or informal writing.
Example Transformation:
- Formal: “The case to which she referred is complex.”
- Informal: “The case she referred to is complex.”
Formal vs. Informal English
| Meaning | Formal | Informal |
|---|---|---|
| Location | “The room in which they met.” | “The room they met in.” |
| Time | “The day on which he arrived.” | “The day he arrived on.” |
| Reason | “The reason for which I called.” | “Why I called.” |
| Belonging | “The topic of which we spoke.” | “The topic we spoke about.” |
“In which” sounds academic; “where” sounds conversational.
Use “in which” in essays, research, and professional writing.
Common Errors and How to Avoid Them
| Mistake | Why It’s Wrong | Correct Form |
|---|---|---|
| “The day in where I met him.” | Mixes preposition and relative adverb incorrectly. | “The day on which I met him.” |
| “The project which he is part.” | Missing preposition. | “The project of which he is part.” |
| “The table that I put my book.” | Missing preposition. | “The table on which I put my book.” |
Tips to Avoid Errors:
- Learn which verbs pair with which prepositions (e.g., depend on, consist of, believe in).
- Replace “which” phrases with simpler forms when unsure.
- Read examples from reliable English sources like BBC Learning English or Cambridge Dictionary.
Practice: Real-World Exercises
Try these to master prepositional “which” phrases.
Fill-in-the-Blank
- The country _______ he was born is beautiful.
- The moment _______ I realized my mistake taught me a lesson.
- The team, members _______ are skilled, won easily.
(Answers: in which, at which, of which)
Rewrite Practice
Transform the following informal sentences into formal equivalents:
| Informal | Formal |
|---|---|
| The city I live in is famous. | The city in which I live is famous. |
| The project I’m working on is new. | The project on which I’m working is new. |
Quick Reference Table: Preposition + ‘Which’ Combinations
| Preposition | Common Use | Example | Informal Equivalent |
|---|---|---|---|
| In which | Time, situation, location | “The era in which he lived.” | “The era he lived in.” |
| On which | Surface, day, topic | “The day on which we met.” | “The day we met on.” |
| At which | Specific time/place | “The event at which she spoke.” | “The event she spoke at.” |
| Of which | Possession/part-whole | “The car, the color of which was red.” | “Whose car was red.” |
| For which | Reason/purpose | “The cause for which they fought.” | “Why they fought.” |
| Through which | Process/pathway | “The pipe through which air passes.” | “The pipe air passes through.” |
| By which | Method/means | “The rule by which we operate.” | “The rule we operate by.” |
| From which | Source/origin | “The place from which he came.” | “The place he came from.” |
Case Study: Academic vs. Conversational Use
Let’s compare two short texts describing the same idea.
Formal (Academic Report):
“The process through which the data were collected ensured accuracy. The meeting at which the results were shared demonstrated transparency.”
Conversational (Spoken English):
“The process we collected the data through was accurate. The meeting we shared the results at was open.”
Both are correct, but the first sounds formal and written; the second sounds casual and spoken.
Takeaway:
Use preposition + which forms when writing essays, professional reports, or formal emails. Use stranded prepositions when talking or writing casually.
Frequently Asked Questions (FAQs)
1. Can I always replace ‘in which’ with ‘where’?
Not always. Use “where” only when referring to places.
✅ “The city where I live.”
❌ “The situation where I live.” → Use “in which.”
2. Is it wrong to end a sentence with a preposition?
No. Ending with a preposition is perfectly acceptable in modern English.
“The topic I was thinking about” is fine.
Formal writing prefers fronting:
“The topic about which I was thinking.”
3. What’s the difference between ‘of which’ and ‘whose’?
Both show possession, but “whose” usually refers to people, “of which” to things.
“The book, of which the pages were torn.”
“The man, whose coat was missing.”
4. Which is more formal — ‘at which’ or ‘where’?
‘At which’ is more formal.
Use it in reports, academic writing, and official contexts.
Use ‘where’ in everyday conversation.
5. How can I remember which preposition to use?
Link prepositions to the verbs or nouns they belong to.
For instance:
- depend on, arrive at, believe in, reason for.
Then add “which” to form the phrase naturally:
“The reason for which I called.”
“The place at which we arrived.”
Conclusion
Mastering prepositional “which” phrases takes time, but it’s worth it. They make your writing clearer, more elegant, and more professional.
Read widely. Notice how authors, journalists, and academics use phrases like “by which” or “through which.” Imitate those structures, practice with your own sentences, and your fluency will grow.
Remember:
“The difference between good English and great English often lies in the tiny words.”
I’m Sameer — a passionate English enthusiast who loves exploring words, grammar, and the art of effective communication. ✍️