(This was originally posted on Curious Fictions on January 21, 2021 -- part of my effort to save things before the site goes away!)

A brilliant writer friend of mine (whom I am not sure would wish to be identified by name here?) asked me an interesting, as well as timely, question this morning: "Do you have any tactics for identifying a novella-sized concept?"
I wrote back, "For all of my novellas, I didn't write them intentionally at novella size? I started with a short story (outlined, even!) and for each one they just.......... swelled up to novella size by the time I was done the events in the outline, but not novel size."
Wow, I thought later, re-reading that answer. Really? And look, I know that writing is part alchemy and part engineering, but more and more these days I find myself yearning for more of the engineering side of things. More forethought, more intentionality. Especially as deadlines become more numerous and closer together.
It's one thing to say 'I sneezed and a book came out,' and quite another to say 'I intended to write a novel in X genre, of about Y words, about Z, and that's what I got, and I gave it to the editor who needed it.' I feel like I need to work on the second thing if I want to have an actual publishing career, instead of what I'm currently doing as a hobbyist (writing whatever I want and then trebucheting it at my poor agent with a note saying CAN WE SELL THIS Y/N).
So my current process is:
I outline a short story in seven or eight sentences, mostly what happens and why it had to happen (e.g. A happens, which causes B to declare revenge, which causes C to explode even though D filled it with concrete spheres to forestall just such an eventuality).
I write the events in the outline, using the number of words I feel like I need for the events to make sense to myself and (sometimes) to the characters.
Sometimes this results in a short story.
Sometimes it results in a novella.
So far it has not resulted in a novel.
What I would like the current process to be is:
I outline something of a particular length, containing what happens and why it had to happen, with a goal wordcount and how long each bit should be.
I write the thing and it is the correct length.
As a result, I find myself thinking not so much about what separates a short story from a novel, but what separates a short story from a novella, and what then separates a novella from a novel. I love the novella length and I find myself naturally gravitating towards novellas these days; why is that? Why does the length feel natural, why did I use that word? What subprocesses are running in my back-brain that declare a story to be complete at that in-between length?
(I don't know any of these answers, by the way, I am just thinking out loud on the page here while I eat lunch and also watch a webinar about mycotoxins and their impact on global agriculture.)
I really feel that a novella is not (or shouldn't be) simply a short story that's gotten unkempt or burst its banks because the writer simply 'couldn't' say their piece in fewer words. Over the past couple of years, I've read numerous novellas and for all of my favourites I came away with a strong impression that 'Yes, that was exactly the correct length, this was destined to be a novella, it would not have worked as a short story, it would not have worked as a novel.'
So based on those (as well as some but not all of my own work) I am going to tentatively essay that a great, intentional novella has some of the following characteristics:
Is based on a premise or concept that is more involved or complex than the one that would form the foundation of a short story.
Requires more world-building than a short story (particularly in spec fic, but also in realist fic) for the reader to understand the premise and why the premise is logical for the world of the story. However, it doesn't require as much as a novel because a) fewer actual events requiring exposition are happening and b) like a short story, it can rely on reader inference and imagination.
Needs more characters to act out the premise and the sequence of events than a short story, in which, generally, an editor will make a face if there's more than about one or two named characters per thousand words.
Can have a major story arc, in which the arcs of all the major characters and events fit, but unlike a short story, also has room for multiple minor arcs that give information, meaning, and momentum to the main arc. But these minor arcs might not need to be as developed or extensive as full 'subplots,' as they would in a novel.
In particular, these minor arcs are easier to wrap up than the subplots of a novel, because they are interacting with fewer things in the smaller world of the novella.
Has room to have more than one tone/mood/style (what I like to refer to as 'the vibe') within reason, whereas a short story works best for me if it has a single, easily-identifiable one, and a novel can vary between different scenes/chapters as well as having an overarching vibe.
Feels 'scaled' correctly to a reader regardless of genre or even sub-genre: a space opera novella doesn't concern itself with every single battle of the past thousand years; an epic fantasy novella doesn't describe the diplomatic relationships of every single kingdom.
Contains scenes of a number and size that can fit into the size of a novella without feeling rushed or cramped. And I know this one is really subjective, but at the same time, you know and I know a reader can pick up a scene and weigh it in their hand and say 'This is really heavy' or 'This is really fluffy.' So, when we trust the reader, we know a novel has room for many of both kinds, but a novella needs to be extremely selective about the balance of weights and whether it's worth the risk to pacing to load it with too many of one or the other. And a short story, of course, can only have a handful of scenes total, so if it's mostly fluff it can probably only manage one really heavy scene, and if it's mostly heavy it can probably only manage one really fluffy scene.
When I say 'premise' or 'concept' what I mean is the most general 'What if/however' question that is asked by the story. For example, for my upcoming novella 'The Annual Migration of Clouds,' the premise is 'What if you got the chance to escape a world that had been devastated by plagues and disaster, but at a cost to yourself and your family?'
(The moment I started talking about scale I also thought YES, WHERE ARE MY CRAYONS, WHERE IS MY SINGLE RAGGEDY DESK SHARPIE, so that's the image here.)
Short story: A couch, which we assume to be in one of the places couches often go, though where it actually exists is left up to us
Novella: A couch, situated clearly in a living room, with other small pieces of furniture around it (though the couch dominates the room), on a rug, next to a window showing us a limited view of a larger and more complex outside world
Novel: A house, situated in the outside world, in which we can safely assume there is a couch but also furniture that is larger or smaller than a couch
I guess I'm back in hand-wavey woo-woo territory, but I've always felt that stories have needs that are unrelated to what we, their creators, need from them; so for instance I talk a lot about the way voice needs to vary from story to story (for example, in 'At the Hand of Every Beast,' the writing had to be stiff, formal, and even a little distant; zippy modern prose would have been all wrong for the story being told).
In the same way, I feel like a story will somehow indicate whether its events need the actions of more or fewer characters to occur, whether it needs more or less room for description and exposition, whether it needs more or fewer settings. (Naturally, it isn't a story's fault if I can't interpret all its requests, or if I hear them only distantly. Or if I ignore them.) The best novellas want to be novellas, and they have needs that cannot be satisfied by a short story or a novel.
The difficulty there is that due to (ironically) economies of scale and distribution, printing standards, and publisher profit margins (sigh), a novella, even one on the longer end, is still not always 'marketable,' in the sense that the majority of publishers would still rather put out, and charge for, novels. With that said though, in just the five-ish years I've been learning about traditional publishing, the novella market has expanded hugely, and it's been very gratifying to see publishers begin to accept, even solicit, novellas, and in some cases open up sub-imprints just for novellas. I think it's a fantastic length for all of us who love stories (that is, the reader, the writer, and the story itself) and I hope the trend continues!