For those of you that don't know, I'm currently helping to organize an anthology. I'm in an interesting place with it, a place that I feel often goes unfilled. I'm not the head editor, I'm more of a go-between and trouble shooter. Its fun, and has me talking to a lot of other authors.
This piece is inspired by a conversation I had with a relatively new author who shows promise, but didn't fully grasp how a short story was different from a chapter. This individual wanted to write up a chapter from a novel that had not yet been written, and submit that as a short story. We had a long talk where I tried to explain the difference, and I am going to continue to do so here because, when I searched for blog posts by someone else on this, there was nothing there.
At the most basic; a short story needs to stand on its own while a chapter is part of a larger beast. There have been a number of instances where a chapter in a novel is also a short story; Gaiman's asides in American Gods where we get small snippets of the rest of the world, some of GRR Martin's prologues and epilogues are short stories in a way, and others. So, we have it like squares and rectangles. A chapter can be a short story, but not all chapters are short stories.
It is actually difficult to explain something so basic; the plot of a novel goes through rising and falling action until we reach the climax, and a short story needs to do all that but more quickly. It needs to be complete. The examples I discussed above meet this odd requirement; they are certainly better for the surrounding universe, but many could stand on their own. And that's okay.
There is still a difference here though; and its a surprisingly slippery one you attempt, obstinately, to drill down to a lower level of definition. In terms of the theoretical frameworks that have been developed; a short story is just a smaller, more simple, novel. Its still a story. They focus on one thing though; one major conflict or some other way to constrain and bind it to something smaller than a novel.
A chapter is part of something larger. It is part of the building of the novel's larger structure of tension and rising conflict. If you write a short story that also serves as a chapter, it is much harder for it to stand on its own as a short story. It can be done, but with so many other limitations in place, it can't help but make it more difficult.
And... that's it. There is no great revelation. People far greater than I have attempted to explain these things using complex theories. They are different and need to be treated as such. I'm hoping that the author I spoke with can make some more sense out of all this, and is able to create something beautiful.