"in which language" is correct and usable in written English.
It is used to indicate which language is being spoken about. For example, "I'm not sure in which language I should use to take the exam."
What does "Nabuur" mean and in which language?
Also, I don't know in which language to thank her.
He cautions against confusing the "many ways in which language connects to thought".
Sometimes Paul likes to imagine a world in which language has disappeared altogether.
It's one of those rare, shiver-making instances in which language seems to become truly physical.
A thrilling work, in which language seems to become truly physical (1 30).
The problem stems from the subtle ways in which language develops.
A thrilling work, directed with intense focus by Mike Bradwell, in which language seems to become truly physical (1 30).
He himself phrases it beautifully: "Fiction… is a kind of religious meditation in which language is the final enlightenment".
They receive a letter informing them where they will live and in which language they will minister.
Revolt's mischievous vignettes are rarely anything other than frank about the ways in which language and behaviour confine women.
