to exchange things between something and something else means that something takes in one kind of thing from that something else and expels another kind of thing into that something else
separated_thing is divided_thing. else is river. separated_thing is not divided_thing. change is when_one_thing_becomes_another_thing. another_way_to_say_separates_things is not divides_objects. space is what_between_else. space is not what_between_else. directions_to_get_somewhere is not how_to_thing. change is not when_one_thing_becomes_another_thing. another_way_to_say_separates_things is divides_objects.