How do you distinguish between a novel and a short story?

[Leopard]

They're often spoken of as two different literary forms, but there seems to be no widespread agreement about how short a short story needs to be. Where do you draw the line between them?

[Calidore]

There are no ironclad standards AFAIK, but the Science Fiction and Fantasy Writers of America use the following guidelines for their Nebula Awards:

Novel: Over 40,000 words
Novella: 17,500 to 40,000 words
Novelette: 7,500 to 17,500 words
Short story: Under 7,500 words

[ennison]

In addition to Calidore's def above. Short story: can be read at one sitting (under an hour); has very few characters; has one significant incident; covers a limited period of time within the narrative.

[Secret III]

Personally I would say a short story can fit into a spineless book such as a magazine or pamphlet while a full-fledged novel is best enjoyed within a hardcover so that you can easily read it. I would say you could also describe a story as a "quarter novel" or a ""third novel" because it isn't short anymore but it cannot stand alone within a hard cover, but the terminologists aren't going to listen to me, so what Calidore said.

My standard for a novel is 80,000 words, minimum.

[Pompey Bum]

A short story makes a point about one significant idea--typically showing its implication. That is the only plot it really requires. Its brevity makes the idea and especially the implication more pointed. A novel is--well a novel. It's as different a literary form as a poem or a play is.