There's no set rule for what constitutes a short story/novella/novel, and generally, a novella will be marketed as a novel by its publishers, since the idea of a "novel" sells better. If you want something to bide by, there's this:
A reasonable estimation.
The other Hemingway I've read was The Old Man and the Sea, which I consumed when I was 14. I hated it, but, again, I was 14. Also, I acquired A Moveable Feast at the same time I did The Sun Also Rises, so I will get to that one soon.