A novelette is considered by most publisher
s to be a piece of mid-length fiction
between 7500 and 17,500 words
in length. Any story
under that size is considered a short story
, and anything longer a novella
The novelette and novella are considered by many to be the "natural" length for many science fiction stories due to SF authors needing a bit more space to adequately create a good settings for the reader and (in the case of hard SF ) to incorporate technical detail about how the new technologies etc. work in said futuristic/alien world.
Unfortunately, many magazines, webzines, and anthologies don't publish work in the novelette range, and those that do may be reluctant to accept such work from unknown authors because a single novelette may cost a big chunk of their fiction budget for an issue and not attract many new readers to compensate. So, beginning writers will find their mid-length work harder to place than their short work.