In
terms of length, word count is typically anywhere from 1,000 to 4,000 for short
stories, however some have 20,000 words and are still classed as short stories.
Stories of fewer than 1,000 words are sometimes referred to as "short
short stories", or "flash fiction".
A novella is a text of
written, fictional, narrative prose normally longer than a short story but shorter than a novel, somewhere between 17,500 and 40,000 words.
A novel is a
relatively long work of narrative fiction, normally written in prose form, and which is typically published as a book.