What Are Relative Clauses with Prepositions?
A relative clause gives extra information about a noun. When we use a preposition in a relative clause, it connects the relative clause to the main sentence. The preposition comes before the relative pronoun (which, whom, that, where) or after the verb. For example: "The café where I study is quiet" uses the preposition in the relative clause to tell us about the location.
Two Patterns: Preposition Before or After
In formal English, the preposition usually comes before the relative pronoun: "The person to whom you spoke is my manager." In everyday English, the preposition often comes at the end of the clause: "The person you spoke to is my manager." Both are correct, but the first style is more formal. At B1 level, you should recognize both patterns and use whichever feels natural for your situation.
Common Prepositions in Relative Clauses
Popular prepositions include: in, at, to, from, with, about, for, and by. You might say: "The movie I'm excited about" (informal), or "The movie about which I am excited" (formal). The choice depends on context. In conversations and emails, the informal style is preferred. In academic writing or formal situations, use the formal pattern with the preposition before the relative pronoun.
Formal vs. Informal Preposition Placement: Side-by-Side Comparison
| Category | Formal Preposition Placement (Preposition before relative pronoun) |
Informal Preposition Placement (Preposition at end of clause) |
|---|---|---|
| Form | Preposition + whom / which The preposition is moved to the front of the relative pronoun. Only whom (for people) and which (for things) are used — never that or who. |
who / that / which + preposition at end The relative pronoun comes directly after the noun, and the preposition is left "stranded" at the end of the clause. That, who, or which can all be used. |
| When to Use | Used in formal writing, academic texts, legal documents, and formal speech. Considered grammatically traditional and is preferred in British formal style. | Used in everyday conversation, informal writing, emails, and casual speech. More natural-sounding to most modern speakers of English. |
| Positive Example | This is the colleague with whom I worked for many years. The report on which she based her findings was outdated. |
This is the colleague who / that I worked with for many years. The report that / which she based her findings on was outdated. |
| Negative Example | The manager for whom she did not work was still critical of her performance. The plan to which they did not agree was cancelled. |
The manager who / that she didn't work for was still critical of her performance. The plan that / which they didn't agree to was cancelled. |
| Question Example | Do you know the person to whom I should speak? Is this the project on which you have been working? |
Do you know the person who / that I should speak to? Is this the project that / which you have been working on? |
| Key Signal Words / Pronouns Allowed | whom (people), which (things) ⚠️ that and who cannot follow a preposition in this pattern. ✗ the book in that I read — incorrect |
who, that, which (all acceptable) ✔ The pronoun can even be omitted when it is the object: the colleague I worked with (zero relative pronoun) |
| 🔑 Key Difference: In formal English, the preposition is placed before the relative pronoun (with whom, on which), and only whom or which may be used — never that. In informal English, the preposition is "stranded" at the end of the clause (who I worked with, that she based her findings on), and a wider range of pronouns — including who, that, which, or even zero pronoun — is acceptable. Both patterns are grammatically correct; the choice depends on the level of formality required. | ||
Formula
Formula
Noun
+
preposition + relative pronoun
+
verb
+
rest of clause
The girl to whom he gave the flowers is my sister.
Examples
The hotel in which we stayed was very comfortable.
Formal style · Preposition before relative pronoun
The hotel we stayed in was very comfortable.
Informal style · Preposition at end
The person to whom you should speak is over there.
Formal style · Everyday usage
The person you should speak to is over there.
Informal style · Conversation
The problem I'm worried about is the cost.
Informal style · Common preposition
The topic which the teacher was talking about was difficult.
Mixed style · Possible in both formal and informal
When to use it
Conversation
In everyday speech, put the preposition at the end of the relative clause. This sounds natural and is easy to understand.
"The friend I went to the cinema with" instead of "the friend with whom I went to the cinema."
Academic Writing
In essays and formal documents, place the preposition before the relative pronoun for a more sophisticated style.
"The research on which this study is based" (formal academic style)
Professional Email
Use either pattern, depending on the level of formality. For important or official communication, prefer preposition-first.
"The project for which we applied has been approved."
Describing Places
Use where instead of in/at + which to describe locations more naturally.
"The city where I grew up is very beautiful."
Signal words
which
whom
that
where
when
whose
preposition + relative pronoun
at the end of the clause
Common Mistakes
✕
Wrong
The person which I spoke with is my teacher.
✓
Correct
The person whom I spoke with is my teacher.
Use 'whom' for people, not 'which'. 'Which' is for things only.
✕
Wrong
The shop in that I bought this is closed.
✓
Correct
The shop in which I bought this is closed.
'That' cannot follow a preposition. Use 'which' after prepositions in formal style.
✕
Wrong
The company for I work is very large.
✓
Correct
The company for which I work is very large.
Prepositions need a relative pronoun. Add 'which' after the preposition.
✕
Wrong
The reason about that I called is important.
✓
Correct
The reason (that) I called is important.
Don't use 'about that'. Either remove the preposition or use the informal style: 'the reason I called about.'
KEY TAKEAWAYS
What to Remember
- A relative clause adds extra information about a noun in the main sentence.
- Prepositions in relative clauses can come before the relative pronoun (formal) or after the verb (informal).
- In formal English, place the preposition directly before which, whom, or where in the clause.
- The preposition connects the relative clause to the main sentence and shows the relationship between ideas.
- Remember: "to whom" and "in which" are common formal patterns; avoid ending with prepositions in formal writing.