As with science fiction, definitions of fantasy fiction vary considerably. I prefer to define it as fiction based on out-and-out magic. Some tales incorporate both science and magic. For example, Marion Zimmer Bradley's works mix magic with technology like spaceships and energy weapons, which is why I classify them as science fiction.

The best known works that rely on out-and-out magic are probably by Tolkien. Others include Ursula LeGuin's Earthsea stories and the saga of Robert E. Howard's character Conan the Barbarian. Such tales frequently involve edged weapons, and are often placed in the "sword and sorcery" subgenre. Tales of animals who talk and act like humans — as do the deer in Fire Bringer — are also fantasy, while the mutant otters of The Demon Breed by James H. Schmitz are not.