Fantasy discussion

I was thinking... How do you define fantasy? What do you think makes a novel a fantasy book, rather than science fiction, or some other genre? Aside from obvious tropes and markers (dragons + monarchy + quest to save the world), I mean. Is it the presence of magic? Is it a setting that has the semblance of human past, however flimsy? Any setting that's not contemporary or historical, and lacks obvious science fiction markers, like advanced technology, space-faring or other forms of futurism?

I'm asking because I'm curious, but also because I'm working (on and off) on a story that I'm not sure if I could define as fantasy or not. It has no magic, the mythology is no more real or cohesive than human mythologies, all the characters are human. Yet it takes place in a world that is more or less obviously not Earth, and makes no mention of Earth or of human civilization as we know it. Ostensibly, it and our world are mutually exclusive. It's also lacking in any of the traditional fantasy plots; more of a family drama than anything else.