Under cinema’s spell
The realm of fantasy is a very wide one. In fact, its definition, when it comes to art, tends to depend on the artistic field. Pierre-George Castex defines it as "the brutal intrusion of mystery in real life". This is the generic conception. Now if we try to narrow it down to the cinematographic field, a film of fantasy can just as well be one of science fiction as a horror movie. The point is to build the story on supernatural elements, from the world of magic and imagination. It doesn’t matter if the result is Alien or Harry Potter, it will still be a fantasy movie.