There’s a difference between these two genres, and it’s a difference that I learn more every day. I called myself a science fiction writer, but I’m really the latter.
They share a similarity, in that their original genesis is a basis in scientific concepts — but that’s where they diverge. Good stories are the ones in which the characters are ultimately more important, but in science fiction the science has a basis in aspects that can be explained — at least extrapolated.
Science fiction can be further divided into hard and soft varieties, but that’s a separate article for the point of this piece.
Where science fantasy differs is that there is no rational explanation of things. This is why Roger Zelazny’s Amber series and Robert Heinlein’s novels are really in different categories.
As I said my current stories are science fantasy; I deal with ghosts. There’s no scientific rationale for their existence — but that isn’t a reason for me not to write this story.
Ironically, I had no interest in the sciences in high school (except for astronomy) — but my writing interest is science fiction, for both reading and writing. I guess my interest in astronomy helps for the writing…
So my current Work in Progress (WIP) is really science fantasy, not science fiction.