What are the main differences between a novelette, a novella, and a novel? As they sound fairly similar.
(Thanks to @Standback for making edits)
It's to do with how much content there is.
A novelette is longer than a short story, but shorter than a novella. The word count is usually between 7,500 words to 17,500 words.
A novella is longer than a novelette and is sometimes called a long short story or a short novel
A novel is longer than a novella and is meant to be read over several days
The reason they sound so familiar is that they all come from the Italian word "novella," feminine of "novello," which means "new."
There are no hard-and-fast rules about where the boundaries lie between the forms. This can differ by genre and by simple established convention in readership (for example, readers now expect novels to be much longer than the ~40,000-odd words they used to be).
Short Stories: up to 7,500 words
Novellettes: 7,500 - 17,000
Novellas: 17,000 - 40,000
Novels: 40,000 + words