Science fiction comedy (sci-fi comedy) or comic science fiction is a subgenre of science fiction or science fantasy that exploits the science-fiction (SF) genre's conventions for comedic effect. Comic science fiction often mocks or satirizes standard SF conventions – such as alien invasion of Earth, interstellar travel, or futuristic technology. It can also satirize and criticize present-day society. Terry Pratchett's 1981 novel Strata also exemplifies the comic science fiction genre.