It is not non-controversial to include zero in the set of whole numbers. A square with side n, where n=0 would be a point. Except it wouldn't, because we have

It is not non-controversial to include zero in the set of whole numbers. A square with side n, where n=0 would be a point. Except it wouldn't, because we have to define these things differently, or geometry would be incoherent. Incidentally, there is no need for a [sic] there because you only need one side to define a square.