William Wilson's single use of "Science Fiction" in his 1851 discussion of "the poetry of science" (in A Little Earnest Book Upon a Great Old Subject) was not the birth of a term but the contingent juxtaposition of two words which happened to join that once and which then, as far as we know, separated for the next seventy-two years, until, on the American shore of the Atlantic, they joined more permanently as a more euphonious replacement for Gernsback's term "scientifiction" in the 1923 letter columns of his "Amazing Stories" magazine—the term we use today, "science fiction" (no caps, unlike Wilson's)—until it had sedimented as the accepted one for that rhetorically identifiable genre—but wholly undefinable one as is every other genre (poetry, history, drama, non-fiction . . .) of fecund and fascinating pulp fictions that would effloress into the variety of texts we have today.

Here is a way to describe (not define: SF CAN'T BE DEFINED, and anyone one who tries knows nothing of the history of fannish criticism or of academic, where the term definition fell out of serious literary analysis by the beginning of the 1950's and was pretty much gone by 1968, everywhere BUT in science fiction criticism where the academic and the fannish mutually supported an appalingly bad habit: today it only survives in discussions of SF) science fiction: if a knowledgable and broadly read SF fan would seriously consider nominating a given text for a Hugo, the chances are large that it's science fiction.That describes one sufficient condition for a text to be science fiction. Alas, there are no necessary ones. And thus looking for definitions, especially formal ones, is a waste of time.

Science fiction criticism is healthiest when people are reading it (SF and SF criticism both) and describing interesting things they have observed about what they read and the world. And it can be rocket science as easily as it can be linguistics or gender studies or disability studies or political science, higher mathematics or the lower fractal productions of diaphantine equations. Or lots of other fields—like botany, ecology, or garbage reclamation or the relationship of sex and cell-phones—in which to have experiences and write about them as well as you can. You can write about groups and differently provisioned persons, both groups and individuals reacting to new landscapes.

Science fiction is the genre in which you can take any notion that even leans toward becoming a rule in the creative writing workshop and break it flagrantly in pursuit on an interesting tale.

Samuel R Delany, from his Facebook page