A novel has many things that a short story doesn't have.
First of all, we can notice the difference in length - novels are much longer than short stories.
Secondly, there are more plots and events in a novel than in a short story - short stories tend to revolve around one particular event.
Thirdly, there are usually more characters in a novel than in a short story, given that you cannot portray many characters deeply within the limited number of pages in a short story, whereas in a novel, you can write as much as you can.