The phrase "in which" is used to indicate the relationship between a specific situation and the actions or events described. It typically introduces a clause that provides more information about the subject or object being discussed, such as a location, a scenario, or a particular context.
The phrase "in which" combines the preposition "in," which comes from Old English "in," meaning "inside" or "within," and "which," derived from Old English "hwilc," used for questioning or specifying among a choice.