Science fiction is the literature of our times, the fuel of our imaginations and the source of our favorite imaginary worlds. But what do we mean when we talk about "science fiction?" Here are some of the many definitions.

"Science fiction is what we point to when we say it." β€” Damon Knight.

"Science fiction is the branch of literature that deals with the effects of change on people in the real world as it can be projected into the past, the future, or to distant places. It often concerns itself with scientific or technological change, and it usually involves matters whose importance is greater than the individual or the community; often civilization or the race itself is in danger." β€” James E. Gunn, "Towards A Definition Of Science Fiction" in Speculations On Speculation. (The whole essay, grappling with the inadequacy of that definition, is worth reading, and most of it is here.)

"Science fiction is the search for a definition of mankind and his status in the universe which will stand in our advanced but confused state of knowledge (science), and is characteristically cast in the Gothic or post Gothic mode." β€” Brian W. Aldiss (with David Wingrove), The Trillion Year Spree.


"My briefest ever definition of science fiction is 'Hubris clobbered by Nemesis.'" β€” Brian W. Aldiss, Science Fiction Art, quoted in Science Fiction Quotations: From The Inner Mind To The Outer Limits, edited by Gary Westfahl.

"Science Fiction is an argument with the universe." - Farah Mendelsohn, in Foundation: The International Review of Science Fiction, issue 88, quoted in Science Fiction Quotations: From The Inner Mind To The Outer Limits, edited by Gary Westfahl.


"Science fiction in general β€” through its long history in different contexts β€” can be defined as 'a literary genre whose necessary and sufficient conditions are the presence and interaction of estrangement and cognition, and whose main formal device is an imagnative framework alternative to the author's empirical environment.'" β€” Darko Suvin.

"Science fiction is not a unitary genre or form, hence cannot be encompassed in a single defintion. It is an assemblage of genres and subgenres that are not intrinsically closely related, but are generally accepted as an area of publication by a marketplace. Science fiction is thus only a commercial term." β€” Everett K. Bleiler, Science-Fiction: The Early Years.


"Science-fiction ... can be defined as: Imaginative extrapolation of true natural phenomena, existing now, or likely to exist in the future." β€” Hugo Gernsback.

"Many people have tried to define science fiction. I like to call it the literature of exploration and change. While other genres obsess upon so-called eternal verities, SF deals with the possibility that our children may have different problems. They may, indeed, be different than we have been." β€” David Brin, Through Stranger Eyes: Reviews, Introductions, Tributes & Iconoclastic Essays.


"I define science fiction as the art of the possible. Fantasy is the art of the impossible. Science fiction, again, is the history of ideas, and they're always ideas that work themselves out and become real and happen in the world. And fantasy comes along and says, 'We're going to break all the laws of physics.' ... Most people don't realize it, but the series of films which have made more money than any other series of films in the history of the universe is the James Bond series. They're all science fiction, too β€” romantic, adventurous, frivolous, fantastic science fiction!" β€” Ray Bradbury, quoted in Conversations With Ray Bradbury by Ray Bradbury and Steven L. Aggelis.

"[Science fiction is] a specialized type of fantasy, in which the prime assumption usually is a new scientific discovery or invention." Jack Williamson, "The Logic Of Fantasy"


"The brightest minds in our field have been trying to find a definition of science fiction for these past seventy years. The short answer is, science fiction stories are given as possible, not necessarily here and now, but somewhere, sometime." β€” Larry Niven, Scatterbrain.

"[A] science fiction story is one which presupposes a technology, or an effect of technology, or a disturbance in the natural order, such as humanity, up to the time of writing, has not in actual fact, experienced." β€” Edmund Crispin, introduction to Best Science Fiction Stories, 1955.


"When people ask me to define science fiction and fantasy I say they are the literatures that explore the fact that we are toolmakers and users, and are always changing our environment." β€” Nalo Hopkinson, quoted in What's a Black Critic To Do?: Interviews, Profiles and Reviews of Black Writers by Donna Bailey Nurse.

"Science fiction is a prose narrative which describes or depicts some aspect or development which does not exist at the time of writing; one significant subgroup of science fiction additionally includes language which either describes scientific fact or explains or reflects the process of scientific thought." β€” Gary Westfahl, The Mechanics of Wonder: The Creation of the Idea of Science Fiction.


"There is only one definition of science fiction that seems to make sense: 'Science fiction is anything published as science fiction.'" β€” Norman Spinrad

"[Science fiction is] a mode of romance with a strong inherent tendency to myth." β€” Northrop Frye.

"[Social] science fiction is that branch of literature which is concerned with the impact of scientific advance on human beings." β€” Isaac Asimov, Science Fiction Writers of America Bulletin, 1951


"I define science fiction as fiction in which things happen that are not possible today β€” that depend, for instance, on advanced space travel, time travel, the discovery of green monsters on other planets or galaxies, or that contain various technologies we have not yet developed." β€” Margaret Atwood, Writing With Intent: Essays, Reviews, Personal Prose: 1983-2005.


"A science fiction story is a story built around human beings, with a human problem and a human solution, which would not have happened at all without its scientific content." β€” Theodore Sturgeon, quoted in A Saucer Of Loneliness: The Complete Stories of Theodore Sturgeon.

"Asked to define science fiction, she said, 'It doesn't really mean anything at all, except that if you use science, you should use it correctly, and if you use your imagination to extend it beyond what we already know, you should do that intelligently.' Butler believed that SF writers could not be put in one box. 'Some look for technological solutions and others disparage technological solutions,' she said. 'Some write about the problems that I write about, and others write about other problems. Some think the world will go to hell and others think it will turn into ice cream. You have the same wide variety in science fiction that you have any place." β€” Octavia Butler, quoted in Popular Contemporary Writers, edited by Michael D. Sharp.

"Science fiction films are not about science. They are about disaster, which is one of the oldest subjects of art." β€” Susan Sontag.


"SF is a controlled way to think and dream about the future. An integration of the mood and attitude of science (the objective universe) with the fears and hopes that spring from the unconscious. Anything that turns you and your social context, the social you, inside out. Nightmares and visions, always outlined by the barely possible." β€” Gregory Benford, quoted at

"[Science fiction is] that class of prose narrative treating of a situation that could not arise in the world we know, but which is hypothesised on the basis of some innovation in science or technology, or pseudo-science or pseudo-technology, whether human or extra-terrestrial in origin." β€” Kingsley Amis.


"[Science fiction is] the attempt to deal rationally with alternate possibilities in a manner which will be entertaining." β€” Lester Del Rey, The World Of Science Fiction 1929-1976: The History Of A Subculture.


"Science fiction, as I mentioned before, writes about what is neither impossible nor possible; the fact is that, when the question of possibility comes up in science fiction, the author can only reply that nobody knows. We haven't been there yet. We haven't discovered that yet. Science fiction hasn't happened." β€” Joanna Russ, To Write Like a Woman: Essays in Feminism and Science Fiction.

"Frederik Pohl's working definition of science fiction when he was editor of Galaxy, he has said, was a story he could publish in the magazine without having too many readers cancel their subscriptions." β€” James E. Gunn, The Road To Science Fiction: From Wells to Heinlein.

"As its best, SF is the medium in which our miserable certainty that tomorrow will be different from today in ways we cant predict, can be transmuted to a sense of excitement and anticipation, occasionally evolving into awe. Poised between intransigent scepticism and uncritical credulity, it is par excellence the literature of the open mind." β€” John Brunner, quoted at


"Science fiction is essentially a kind of fiction in which people learn more about how to live in the real world, visiting imaginary worlds unlike our own, in order to investigate by way of pleasurable thought-experiments how things might be done differently. " β€” Brian Stableford, Guest of Honor speech at ConFuse 1991, quoted at

"I would define science fiction as a form of literature which crosses the frontiers of knoweldge using imagination, intuition or logic to guide it. At times correct scientific or technical detail is demanded by an exacting readership; where the story goes beyond known facts, the deductions must be feasible or at least not in obvious conflict with accepted theories." β€” Ian S. Menzies, "Trends In Science Fiction," New Scientist, 18 September 1958.


"Attempting to define science fiction is an undertaking almost as difficult, though not so popular, as trying to define pornography... In both pornography and SF, the problem lies in knowing exactly where to draw the line." β€” Arthur C. Clarke, Greetings, Carbon-Based Bipeds!: Collected Essays, 1934-1998.

Top image: Untitled Future Mutation by Luke Jerram, photo by Luke Jerram, from Jerram's Glass Microbiology sculpture project.