1. What is a novel?
A novel is a work longer than a short story and normally involving weightier subjects or more involved action. The length has varied throughout the last century, mostly in response to technology. The people of NANOWRIMO* set their length for a completed novel at fifty thousand words. When they did this, you could not get a fifty thousand word novel published anywhere. The minimum in the last decade has hovered around eighty thousand. (Some category romances are thinner, but they also tend to be work for hire.)
However, if you read books from the first half of the twentieth century, you’ll find what is sold as a novel is often around fifty thousand words, and could be as low as twenty thousand.
On the other hand, it appeared to be cheaper to print longer works — hence things like the Ace doubles — thus leading to a slow growth in the size of the books.
In the late seventies and early eighties, a fatal intersection of word processing technology, marketing trends, and printing tech created the dreaded goat gagger — a novel so long that the only way to attain it was to combine several novels into one. This ran around two hundred and fifty thousand words, and could be near-deadly to write. Often it was a group adventure with multiple story lines.
The advent of ebooks is pushing things the other way. People perceive books differently on the Kindle, and I’ve bought things called “novels” that were around thirty thousand words and not regretted the purchase.
So if you have anything between thirty thousand and two hundred and fifty thousand words, it can be “a novel.”
The only limitation on the size is if you want to send it to a traditional press. They still prefer works of around a hundred thousand words or more, though the goat gagger has gone out of style.