~PEN TO PAPER~: How long is a novella

So how long is a novella.
If you google the question there are as many answers as words.
So if there isn't a definite then it can be as short or as long as you like.
My formula is this
I write on average 77,000 word novels. So we shall say they are 80,000 in round figures. They have sub plots, more than 4 characters and various situations that need exploring to a conclusion. Back histories and complicated twists.

In contrast.
Mr Tripp will probably come out at 45,000
It will have no sub plot. A linear plot ie. the two protagonists will advance to a conclusion without any interference .
There are a myriad of characters each with small interactions with the two main character and no background of their own except for small introductions.
This novella is from A to B and who the Tripps meet along the way.
Small, compact, funny and a light read.

An Apt pupil by Stephen King was a short story/novella. It revolved around two characters.

Shawshank Redemption was a short story/novella. It had one main character focus.

Mr Blandings builds his dream house by Eric Hodgins was a short story, became a longer story/novella then turned into a movie. It has two main characters who interacted with others, but without their own background and was straight from A to B.

So at 45,000 to 50,000 I think a story can call itself a novella.
Also if it would translate well into an audio book with the criteria of
short,
easily identifiable protagonists and a
progressive story line then I think the title of novella seems in order.
But if you want to take a look at what everyone else is saying then have a look at these.