Define: Horror

I'll be the first to say I don't have an encyclopedic knowledge of all things horror. But then again how easy is it to define any genre? Certainly not all movies use all the same techniques, the same settings, or the same themes.

Geesh, it just hit me that this entry could be a bit lofty for me, but I'll give a stab at it.

Being as general as possible, horror movies build up suspense and try to scare you. They could cover primordial fears, like being eaten alive in, umm, Eaten Alive. Or filmmakers can resort to some unnatural, disturbing creatures. The first thing that comes to mind are those damn flying monkeys in The Wizard of Oz. Seriously that film made AFI's 100 Greatest Thrillers list, along with Alien and The Shining, just because of those airborne simians.

Well, from that mess of a definition movies can be classified into sub-genres. Shaun of the Dead, Cape Fear, and Invasion of the Body Snatchers are all considered horror but are very different from each other. So here's my attempt to identify the major ones:

* Slapstick - This should be pretty obvious but it includes films with an intentional sense of humor. Laughing at any death scene would be a good indication. Ex. Shaun of the Dead, Dead Alive, Planet Terror, Killer Tomatoes Eat France.

* Psychological - There might not be any men in costumes or bloody stumps, but these films are haunting nonetheless. Usually audiences see the workings of a disturbed individual.
Ex. Cape Fear, Peeping Tom, Mad Love, 2001: A Space Odyssey (that'd be HAL who's the crazy one).

* Standard - Ignore the lackluster name, this genre is as good as the others. You've got a person or a group up against a villain/alien race/etc.
Ex. Invasion of the Body Snatchers, Dracula, Creature from the Black Lagoon, The Exorcist

* Torture - A very recent genre that focuses on the gore. Honestly I haven't watched too much of these, but I thought I should still include it.
Ex. Saw, Hostel.

Right now I'm even thinking of movies that don't fit these labels. Oh well. Horror's different to different people. Suggest any modifications/additions to the list. I'll consider anything and everything to get the best definition.