I know that very technical stories like one of Jules Verne's are science fiction, but what about stories of werewolves, etc.I've never heard of fantasy as being a subgenre of science fiction, which is why these questions are rather interesting. Since when have science fiction and fantasy been at all synonymous? They've always seemed to be rather opposite categories to me, connected only by the fact that they both deal with elements of the nonexistent. Science fiction, in theory, looks at these elements through the lens of the possible, while fantasy looks at them through the lens of the impossible. Spaceships are real, while wizards and dragons are not.
Does this count as science fiction? Does it count as fantasy fiction? Is fantasy fiction a subgroup of science fiction?
Answering the question, however, leads me to a bit of a paradox. I've always automatically lumped werewolves in with horror and fantasy, but is it possible that werewolves could be allowed in science? I'm inclined to think so. Perhaps not in the traditional sense that we have seen in the movies, but in a different sense. Werewolves are easily fantastical creatures, yet they could also be scientific creatures. It all depends on how it is done. If the werewolves change because of a curse or "blood" without explanation of why they are genetically the way they are, then it's clearly fantasy or horror (or both). But if the werewolves are explained to be, say, genetic experiments in a government lab, or genetic anomalies explained by mutations in the cells, then they become part of a science fiction universe.
That aside, I was surprised by the response that was chosen as the "best answer" by the questioner (note: I've edited it so it's readable, which will only help to a certain extent):
Sci-fi is a HUGE category. From aliens to elves, wizards to talking animals and everything in between. So, I think that werewolves can be counted as fantasy fiction, and horror like someone else said. Sci-fi is interesting, because it can intertwine itself with many other different genres without getting confusing. Of course, there is the basic story plot that is pretty sci-fi, and then it can venture off into different courses. Horror being one of them. So yeah, it can!Actually, no it can't. You see, here's the problem with this whole discussion. Science fiction isn't fantasy. Fantasy is not a part of science fiction, it's a part of the broader term "speculative fiction." Speculative fiction encompasses all literatures of the fantastic/nonexistent. Fantasy and science fiction each deal with specific forms of speculative fiction. Aliens and elves are not synonymous with the same thing. Aliens are almost exclusively the realm of science fiction while elves are almost exclusively the realm of fantasy, with little exception.
In fact, to make such generalizations is rather ignorant of what the genres actually entail. You can have elves in science fiction, but not Tolkien elves or traditional fantasy elves. The parameters are different for science fiction elves; fantasy elves are not the same as science fiction elves precisely because they follow different rules. Vulcans from Star Trek are science fiction elves and you can clearly see that they aren't the same as the elves that Tolkien created, where magic and enchanted rings exist.
So, while there may be some similarities between the genres, it is important to maintain a separation. The two are, with rare exception, distinct from each other. Without that separation it becomes near impossible to provide appropriate classifications for speculative literatures. If science fiction and fantasy can be anything, then they cease to become categories at all--they cease to be important. Before long, all categories could become unimportant (and trust me when I say this will wreak havoc on book shoppers).