The Science Fiction and Fantasy genres are very often blurred, and, if you don’t set out with the intention of deliberately writing one or the other genre, it can be difficult to categorise a story that has elements of both genres.

Another issue that can arise if you’re not aware of which genre you’re writing is inadvertently breaking the rules of consistency in your story. For example, a few years ago I helped a writer with a story that had begun as Sci Fi (not Science Fiction – more about the difference in a moment), with technology and a being who was able to change shape. The ending of the story, however, switched to Urban Fantasy with the science-based rules of mass and volume being broken in favour of a magical outcome.

Science Fiction

Science Fiction – which is shortened to SF, and never “Sci Fi” – is used to describe hard to medium core science-based fiction. The science forming the background of the book can be hard science, such as nuclear physics, quantum mechanics, chemistry, biology, geology, genetics, robotics, computer programming, etc – or it could be a soft science like psychology, sociology, anthropology, etc.

Whatever the science discipline referenced, it forms a large part of the plot process. The current laws of the discipline must be followed, or if broken, there must be an explanation for the fictional possibility of breaking or bending the laws – for example, Faster Than Light space travel is not yet possible for us, but it is possible that a future or fictional world could have developed a means of “warping” space in order to decrease journey time.

Sci Fi

Sci Fi is the fun version of Science Fiction. The split arose when some science fiction writers either wanted to introduce concepts that would never be possible in any world based on our laws of physics, or writers without a science background began writing science fiction without feeling the need to check their science. Hollywood also played a big role in introducing Sci Fi over Science Fiction when they insisted on special sound effects even in the vacuum of space (Star Trek and Star Wars). Sci Fi is allowed to bend the laws of science for artistic licence, but some hard core Science Fiction writers refuse to be associated with “Sci Fi”, hence SF as the abbreviation for true Science Fiction.

Futuristic

Futuristic fiction is often used to describe fiction that has little scientific reference, but it set in the future. Many soft science based novels are categorised as Futuristic because they don’t seem like science fiction, or publishers are concerned that potential readers may be intimidated or put off if it is classified as science fiction.

Fantasy

Fantasy doesn't have to follow scientific laws, but it must stick to rules of consistency (ie, if a magic trick has certain consequences in chapter one, it must have the same consequences in chapter 16). Fantasy often has a bucolic setting and elements of magic to set it apart from period adventure stories.

Urban fantasy

Urban fantasy can have a contemporary, or even futuristic, setting, but remains fantasy due to breaking of the laws of science (eg, X-Men, Buffy, Charmed). Urban fantasy could be referred to as Sci Fi (or even “Science Fiction/Fantasy”), but generally makes no mention even of pseudo-science or “techno babble”.

Contemporary Fantasy

Urban fantasy is sometimes called “Contemporary Fantasy”, but this usually refers to fiction with characters who don’t have superpowers or invincibility. Harry Potter is a good example of Contemporary Fantasy, because the characters’ use of their magical powers isn’t the sole plot device.

Science Fiction/Fantasy blend

Labelling a book as Science Fiction/Fantasy, or SciFi/Fantasy, is simply an easier way for bookstores and libraries to categorise a lot of books in one section. Often bookstores cannot read enough of each book to tell whether it is true Science Fiction or possibly Urban Fantasy. A broader category means is easier to make it findable for people who are looking for that type of book, rather than mis-shelving it by being too specific.