A cellmate is the person who shares your prison cell — the small locked room you sleep in. You did not pick them, and you may like them or not; the word only says you share that room. You meet it in news and films more than in daily class. Though actually, cell here is the prison room, not a phone and not the tiny living bit inside a body. Mate is the same piece as in roommate: the person you are paired with, not “friend” in a warm way. People sometimes joke that two workers stuck in a tiny office are cellmates, but that is stretching it.

獄友、同房囚犯