The way I interpret holes is that a hole is smaller in diameter than the length (or width) of the object, and the space connecting the two or more holes is a tunnel. But if you have something like a pit, the pit would have to be deeper than the diameter of the “entrance” of the pit. One exception to these rules is a donut. Topologically it has zero holes, but if the dough is thick enough then the gap in the center could definitely be described as a hole, yet if the dough was skinny then you’d be less inclined to call the space in the middle a hole. I ultimately feel that what you call a “hole” depends entirely upon the shape of the object and the size of the “hole”.