A novella, also called a novelette or a short novel, is an extended work of fiction longer than a short story, but shorter than a novel. It typically features more character development or a more extended plot than a short story, but a more focused treatment than a novel.
Commercially, this is considerd an awkward length -- too short for independent publication, but too long for magazine publication. The limits and definitions of the form are somewhat vague, but anything in the range of 35,000 or 40,000 to 60,000 or perhaps 70,000 words will usually be considered a novella by commercial publishers.
- More information on this topic is available at [ Wikipedia:Novella ]