Science fiction involves speculative elements based on established scientific laws or postulated future scientific discoveries. It differs from fantasy in grounding imaginary elements in science. Common themes include settings in the future, outer space, or involving new technology. Popular subgenres include hard science fiction focusing on physics; soft science fiction focusing on social sciences; cyberpunk set in dystopian near-futures dominated by corporations; and space opera featuring large-scale adventures in space. Recurring characters include aliens, cyborgs with enhanced abilities, mutants, espers with psychic powers, and hive minds occupying multiple bodies.

1. Science fiction(Aka sci-fi and SF)

2. Codes and conventions Often involves speculations based on current or future science or technology. Differs from fantasy in that its imaginary elements are largely possible within scientifically established or scientifically postulated laws of nature (though some elements in a story might still be pure imaginative speculation). Largely based on trying to be entertaining but rational about alternate possibilities in settings that are contrary to known reality, including: (i) A setting in the future, in alternative time lines, or in a historical past that contradicts known facts of history or the archaeological record (ii) A setting in outer space, on other worlds, or involving aliens. (iii) Stories that involve technology or scientific principles that contradict known laws of nature. (iv) Stories that involve discovery or application of new scientific principles, such as time travel or psionics (eg. telepathy, telekinesis, etc), or new technology, such as nanotechnology, faster-than-light travel or robots, or of new and different political or social systems (e.g. a dystopia, or a situation where organized society has collapsed). Realistic speculation about possible future events, based solidly on adequate knowledge of the real world, past and present, and on a thorough understanding of the nature and significance of the scientific method, according to science fiction writer Robert A. Heinlein. Fantasy is the impossible made probable. Science Fiction is the improbable made possible, according to Rod Serling, an American screenwriter, best known for his live television dramas of the 1950s and his science fiction anthology TV series, The Twilight Zone. Related genres are Speculative fiction, fantasy, and horror.

3. Sub-genres Hard SF: Characterized by rigorous attention to accurate detail in quantitative sciences, especially physics, astrophysics, and chemistry, or on accurately depicting worlds that more advanced technology may make possible. Many accurate predictions of the future come from the hard science fiction subgenre, but numerous inaccurate predictions have emerged as well. Soft and social SF: Based on social sciences such as psychology, economics, political science, sociology, and anthropology. Stories focus primarily on character and emotion. Two good examples are Wall-E and ET because both films’ stories centre around the titular characters and how they feel about what happens to them.

6. Often complicated by logical problems such as the grandfather paradox (a man travels back in time and kills his biological grandfather before the latter meets the traveller's grandmother. As a result, one of the traveller's parents (and by extension, the traveller himself) is never conceived. This means that he can’t have travelled back in time after all, so the grandfather is still alive, and the traveller is conceived, allowing him to travel back in time and kill his grandfather).

8. Superhuman: Stories deal with the emergence of humans who have abilities beyond the norm. This can stem either from natural causes (accidental modification of the body) or be the result of intentional augmentation (purposeful modification of the body). Stories usually focus on the alienation that these beings feel as well as society's reaction to them. They’ve have played a role in the real life discussion of human enhancement. A good example is X-men. Apocalyptic: Concerned with the end of civilization through nuclear war, plague, or some other general disaster or with a world or civilization after such a disaster. Apocalyptic generally concerns the disaster itself and the direct aftermath, while post-apocalyptic can deal with anything from the near aftermath to hundreds or thousands of years in the future. Good examples of this are the Terminator films.

9. Space opera: Emphasizes romantic, often melodramatic adventure, set mainly or entirely in space, generally involving conflict between opponents possessing powerful (and sometimes quite fanciful) technologies and abilities. The most significant trait is that settings, characters, battles, powers, and themes tend to be very large-scale. The stories typically follow the Homeric (heroic/grand/imposing) tradition, in which a small band of adventurers are cast against larger-than-life backdrops of powerful warring factions. Good examples are the Star Wars films. Space Western: Transposes themes of the American Western books and film to a backdrop of futuristic space frontiers. Stories typically involve "frontier" colony worlds (colonies that have only recently been terraformed (the hypothetical process of deliberately modifying its atmosphere, temperature, surface topography or ecology to be similar to those of Earth to make it habitable by humans) and/or settled) serving as stand-ins for the backdrop of lawlessness and economic expansion that were predominant in the American west. A good example is Serenity.

10. Feminist SF: Tends to deal with women's roles in society. Poses questions about social issues such as how society constructs gender roles, the role reproduction plays in defining gender and the unequal political and personal power of men and women. Stories have illustrated these themes using utopias to explore a society in which gender differences or gender power imbalances do not exist, or dystopias to explore worlds in which gender inequalities are intensified, thus asserting a need for feminist work to continue. Good examples are the Alien films as the protagonist is a strong woman, not the stereotypical damsel in distress. New wave: Stories have a high degree of experimentation, both in form and in content, and a highbrow and self-consciously "literary" or artistic sensibility. Often openly mocks the traditions of pulp science fiction (inexpensive stories for the mass market), which writers and creators of new wave regarde as stodgy, irrelevant and unambitious.

16. Can be good or evil

18. Can be good or evil

19. Has also featured in Star Trek and the Jedis in Star Wars could be considered similar.