“More to the point: the Backshift doesn’t happen only to single words; it happens to pairs of them, and knits them together in the process. An example is the difference between black board and blackboard. A black board is some board that someone painted black. A blackboard is the particular thing made of slate that hangs on a schoolroom wall. Black board is pronounced “black BOARD,” while the thing on the wall is a “BLACK-board,” and that’s no accident. The way we mark blackboard as “a thing,” different from just any old board that happens to be black, is with the Backshift. A blackboard is something very specific—“a thing,” as it were.”