"Something can either be in state A or in state B; it cannot be in both of these states simultaneously, and it cannot be in neither of them. It has to be in one of those two states". What would those two states be called with respect to each other?
For example, something can either be living or dead, it cannot be both or neither at the same time. So the property of being living or dead would be called _________ of each other. It can be called the opposites of each other but that doesn't convey the full meaning. Because "black" and "white" are "opposites", but something can be other than black and white e.g., red. So it fulfills the second condition of not being in both of the states simultaneously but doesn't suffice the first condition of being in either of those states.
For reference, it is called
نقیض(Naqeed) in Arabic. There is a separate word for opposite i.e.,