Why are Sci-Fi and Fantasy often grouped together?

Question: Why are Sci-Fi and Fantasy often grouped together?

Answer: Science fiction and fantasy both allow us to imagine other worlds and other realities besides ours -- to escape the mundane, the earthbound, and the ordinary. Both forms start with a change to the world we see around us, and then use that change as a basis for constructing another reality for its characters to inhabit.

Because of this, science fiction and fantasy are sometimes collectively referred to as speculative fiction. The abbreviation sff, for "science fiction/fantasy," is also sometimes seen.

Another reason these two genres are often grouped together is that some works combine elements of both: two landmark science fiction series, Star Trek and Space: 1999, both assume the possibility of shape-shifters, for example, without attempting to explain them within their own scientific frameworks. Important figures in speculative fiction sometimes switch between genres: Orson Scott Card and Ursula K. Le Guin, to name two examples, have written major works in both fantasy and science fiction.