When science fiction first began a few authors tried translating a standard story, for example a western, to a science fiction milieu. In such a case, they would give different elements of the story science-fictiony names, but that's all they would change. Editors and critics refer to this kind of lazy writing as 'calling a rabbit a smeerp.' Once in a while, we get a story like this. Don't do it!
Ideally, every science fiction story has some uniquely SF element that is crucial to the story. It actually doesn't matter what you call things.
The real trick is to show protagonists deal with this uniqueness in a compelling way that resonates with readers, in a way that evokes emotions in readers.
Speculative fiction has the added challenge that protagonists aren't necessarily human. In fact, the protagonist often isn't human. Think ghost, werewolf, elf, god, alien, robot... You get the idea. I've disagreed with other writers in the past, however, in that I say none of these protagonists are truly not-human. Since readers are human, they need something they can relate to. Do you agree? Disagree?
Send us a story that proves me wrong!
And, oh, yeah, Happy Halloween!