Novels, novellas and short stories are all narratives designed to transport a reader to a fictional world. You would be right to assume that novels are longer than novellas and that novellas are longer than short stories, but the differences in these forms go beyond the number of words required to tell the tale.
Typical Word Lengths
According to "Writer's Digest," a novel can range from 55,000 to 300,000 words, a novella is 30,000 to 50,000 words and a short story is 1,500 to 30,000 words. Notice that the longer short stories border on the length of novellas and the longer novellas border on the length of novels. When word lengths are borderline, the author and publisher can determine whether to market the work as a short story, novella or novel.
Characteristics of Novels
Novels, as the longest form of fiction, give a story plenty of breathing room. Like a short story or novella, a novel presents characters in conflict encountering a series of obstacles. The characters either overcome the obstacles to meet their goals, or they fail to do so and arrive at a resolution at the end. Characters in novels may be more developed than those in shorter works, and they may transform more significantly over the course of the book. Novels also have the page count necessary to create subplots and include minor characters that add texture and depth to the story.
Characteristics of Novellas
Novellas, publishing's neglected middle child, historically received scant attention from the industry. Because shorter word counts make for thinner books with lower cover prices, it was difficult for publishers to make a profit on novellas. However, with the advent of e-readers, novellas are enjoying a surge in popularity. Novellas are the right length for a tale that is more layered and complex than a short story but doesn't require the larger cast of characters or epic scope of a novel.
Characteristics of Short Stories
A short story has a more limited focus than novels or novellas, and the plot is usually tied to one specific chain of events. Because the reader must identify with a character quickly to become engaged, the tale is often told from the protagonist's point of view. Techniques that are effective in a novel, such as varying narrators from chapter to chapter, are not feasible in a short story. Language in short stories is often symbolic and rich in subtext as authors strive to make every word count.