Q: Can you explain to me what “in which” means in the phase “the way in which”? I find that just dropping “in which” or simply replacing it with “that” does the trick admirably.
A: The pronoun “that” has many uses. Among other things, it can be used to mean “in which,” “on which,” “with which,” or “by which.”
For example, the phrase “the way in which” means the same thing as “the way that.”
In these phrases, “in which” is grammatically equivalent to “that.” And, as you say, “way” often works by itself, without adding either “in which” or “that.”
So these sentences have the same meaning: “I didn’t like the way in which he expressed himself” … “I didn’t like the way that he expressed himself” … “I didn’t like the way he expressed himself.”
The sentence you choose here is a matter of preference. A writer is free to pick whatever best conveys the meaning and seems most compatible with what’s being written—its degree of formality and so on.
But with words other than “way,” there are times when “in which” is the natural usage. In none of these sentences, for instance, would you substitute “that” for “in which”:
“John was criticized for the manner in which he left his wife.”
“It was a tumor, in which case surgery was needed.”
“She likes to read German, in which she’s fluent.”
“Diamond-cutting is a task in which a steady hand is called for.”
“There were three accidents last week in which people were killed.”
“In which month is Veterans Day?”
“Fossiliferous stone is rock in which fossils are found.”
“His advice was to sell early, in which he was proved right.”
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