My personal definition is that horror stories must involve isolation, immediate and highly improbable danger (real or perceived), and something that throws off your ability to reason your way out of the situation.
So, I define SotL as a thriller, even though there are horror elements at the end. Jaws is a horror movie.
I like horror movies that don’t rely on jump scares and gore. Both have their place, but movies that are unsettling, where you know something isn’t quite right and you can’t figure out exactly what–those are my favorites.
I think I like this.
Another is it X or is it Y discussion that comes up is the difference between modern horror and urban fantasy/contemporary fantasy. Very often both will involve supernatural creatures and/or monsters. In the fantasy novels fewer people are eaten by the monsters. In thrillers there are fewer deaths than in horror movies. A lot of it has to do with body count, really.
I’ve never given it much thought, but on a gut level, I expect a horror movie to be more gory/disgusting.
“It’s bad enough that they kill you, but then you also get a face full of alien wing-wang.”
When I opened the thread, my first thought was: Thriller = real scary stuff, Horror = make-believe scary stuff. This would put a number of movies typically thought of as horror, like Misery, Saw or Silence of the Lambs, in the thriller section, but I can’t think of many thriller movies that would be shifted to horror.
But now I agree more with RealityChuck that the difference is more about building tension v. sudden frights. Of course, a lot of movies do both quite well (Ringu, Misery). It’s probably never going to be a clear distinction, and if an Official Dividing Line were ever declared, at least a half-dozen film-makers would immediately set out to blur it .