Formal Relative Clauses: In Which, For Whom, and Preposition Placement

English allows two patterns: the colleague I spoke to and the colleague to whom I spoke. The grammar overlaps; the register does not.

Stranding is normal English

Leaving the preposition at the end is standard and often preferred in speech and ordinary prose: the issue we talked about; the company she works for. Avoid the old myth that a sentence is automatically wrong because it ends in a preposition.

Fronting the preposition raises the register

Formal writing may use the conditions under which the trial was conducted or the participants for whom accommodation was required. After a fronted preposition, use whom for people and which for things—not that.

Meaning can change with the preposition

The person with whom I travelled is not the same as the person for whom I travelled. Do not let the relative-clause structure distract you from the lexical relationship created by the preposition.

This topic builds naturally on Who vs Whom vs Whose and defining vs non-defining relatives. At C1, the goal is not to replace every stranded preposition with a formal one. It is to control both options and choose the register that fits.