I use the term “speculative fiction” as a convenient category to refer to any storytelling that isn’t set in the everyday world, or if it is, it presents that world as different in some way. Quoting Wikipedia:
“Speculative fiction is a broad umbrella genre denoting any narrative fiction with supernatural or futuristic elements; this encompasses the genres of science fiction, fantasy, horror, supernatural fiction, science fantasy, and superhero fiction, as well as combinations of the previous genres. It typically strays strongly from reality and so may feature fictional types of beings like mythical creatures and supernatural entities, technologies that do not exist in real life like time machines and interstellar spaceships, or magical or otherwise scientifically inexplicable elements. The term’s popularity is sometimes attributed to Robert Heinlein, who referenced it in 1947 in an editorial essay, although there are prior mentions of speculative fiction, or its variant “speculative literature”.“
However there are other definitions as a simple google search reveals, e.g. speculative fiction may include fantasy but only some science fiction, or science fiction and fantasy but only some horror.
Another definition, by by Claire Light, is that “speculative fiction” (science fiction, fantasy, magical realism, and supernatural horror) contains a new” element of the world or the narrative that does not exist in the real world. Other genres and literary fiction that describes or mimics the “real world” is then called “mimetic fiction”. (see diagram at top of this page).
Mimetic is a great word, but perhaps a bit too academic and obscure sounding. Also, even speculative fiction is very often imitative of the real world; such as in Space Opera, where spacefleets resemble Earth navies, and so on. I would suggest instead the term “Mundane Fiction”, in that it is about the mundane or everyday world. Admittedly, this isn’t perfect eiteher, because mundane could also mean banal or mediocre, which good literary fiction is anything but. Perhaps “Mimetic/Mundane” as the counterpole to “Speculative”
Alternate history – Focusing on historical events as if they happened in a different way, and their implications on the present. Sometimes included under science fiction (The Man In The High Castle), or where there is less emphasis on technology might be considered a variant of historical fiction.
Dystopia – Takes place in a highly undesirable society, often plagued with strict control, violence, chaos, brainwashing and other negative elements. (1984, Brave New World). Overlaps with science fiction, but emphasises more the social than the technological. Young Adult Dystopia is a popular sub-genre (Hunger Games, Divergent, Mazerunner)
Fantasy – Includes elements and beings from human cultural imagination, such as mythical creatures (dragons and fairies, for example), magic and magical elements, sorcery, witchcraft, etc. Subgenres include High Fantasy (Tolkien –The Lord of the Rings), Sword and Sorcery (Conan the Barbarian), Dark Fantasy which overlaps with Horror (Vampires etc), Urban Fantasy (JK Rowling – Harry Potter), New Weird (Neil Gaiman, China Miéville, Jeff VanderMeer, etc)
Horror – somewhat similar to fantasy, but focusing on terrifying, evil and often powerful beings, such as monsters and ghosts. Also aims to transmit actual fear and confusion to the reader/watcher. Subgenres include Fantasy-Horror (originally Vampire Dracula, Nosferatu, The Vampire Lestat, but since including other supernatural creatures) which can equally go in the previous category, Slasher (A Nightmare on Elm Street), Cosmic Horror (Lovecraft – Chthulu mythos), etc
Magical realism – one or two magical or fantastical events take place in the otherwise ordinary real world, with no attempt to explain them or see them as unusual (One Hundred Years of Solitude, by Gabriel García Márquez)
Post-apocalyptic – Focuses on groups of survivors after a massive, typically worldwide disaster. Includes subgenres like apocalyptic (before and during a massive, worldwide disaster. The Day After Tomorrow, 2012), survival (Waterworld, Metro 2033, The Stand, Fallout, Mad Max., etc), Zombie apocalypse and the derivative robopacalypse (overlap with horror and science fiction respectively), while the rebuilding civilisation version (Canticle for Leibowitz, The Postman) is generally included under science fiction.
Science fiction – Features technologies that do not exist in real life (but may be supposed to do in the future), including time travel, interstellar travel, flying cars and also beings and societies from other planets (aliens). Subgenres include Alien Invasion (War of the Worlds, Independence Day), Cyberpunk (Bladerunner, Neuromancer, Schizmatrix), Hard Science Fiction (Mars Trilogy), Military Science Fiction (Starship Troopers, Forever War, Honorverse), Planetary Romance (John Carter on Mars), Space Opera (Star Trek, Star Wars), Science fantasy (fantasy science fiction hybrid, e.g. Star Wars can be considered both space opera and science fantasy), Steampunk (an inter-genre category that can equally be considered Alternative History or fantasy), Time Travel (HG Wells The Time Machine)
Slipstream – non-realistic fiction that crosses conventional genre boundaries between science fiction, fantasy, and literary fiction. Like Magical Realism it uses cognitive dissonance and falls between speculative fiction and mainstream fiction.
Superhero – centers on superheroes with extraordinary abilities or powers and their fight against supervillains. Stories tend to be repetitious and involve a lot of fighting with other superheroes or supervillains. While it may incorporate elements of science fiction, only a cursory attempt is made to explain the absurdities and contradiction of the laws of physics that superheroes involve.
Supernatural romance – mostly young adult, about erotic or romantic relationship between a human and a nonhuman (benevolent vampire, angel, alien, etc). Tends to overlap with or be included under Fantasy or Science Fiction
Utopia Takes place in a highly desirable society, often presented as advanced, happy, intelligent or even perfect or problem-free (Island, Ecotopia). Because everything is so perfect, this is more a didactic device than a storytelling one; fiction tends almost universally to portray utopias as actually dystopias (a rare exception being the Culture Novels of Iain M Banks, which belong under the category of space opera science fiction) .
Visionary Fiction – is a new category that illustrates and demonstrates the process of growth in human consciousness, and Jungian, mystical and other themes. It overlaps with Inspirational fiction or “inspirational writing”. It seems that inspirational fiction is more mainstream Christian based, and Visionary fiction New Age/Human Potential/Alternative religion. There’s also Metaphysical (or Philosophical) Fiction “in which a significant proportion of the work is devoted to a discussion of the sort of questions normally addressed in discursive philosophy. These might include the function and role of society, the purpose of life, ethics or morals, the role of art in human lives, and the role of experience or reason in the development of knowledge.” (Wikipedia). Includes novels by Albert Camus, Herman Hesse, Philip K. Dick, Ayn Rand, and Umberto Eco. My interest however is in metaphysical science fiction