Sci-fi is short for science fiction. For the records, sci-fi can’t be constricted to a particular definition but literally speaking, it is the science of lies or better still, the science of imagination rather than reality.
Sci-fi is largely based on writing rationally about alternative possible worlds or futures. It is similar to, but different from fantasy in that, within the context of the story, its imaginary elements are largely possible within scientifically established or scientifically postulated physical laws though some elements in a story might still
be pure imaginative speculation- lets just say hypothetical.
Sci-fi has been so imbedded into our reality that we don’t see it has an imagination anymore. Most sci-fi relies on a considerable degree of suspension of disbelief, which is facilitated into our minds by potential scientific explanations or solutions to various fictional elements such as:
A time setting in the future, in alternative timelines, or in a historical past that contradicts known facts of history or the archaeological record.
A spatial setting or scenes in outer space, on other worlds, or on subterranean earth .
Characters that include aliens, mutants, androids, or humanoid robots and other types of characters arising from a future human evolution.
Futuristic or plausible technology such as ray guns, teleportation machines, hologram and humanoid computers .
Scientific principles that are new or that contradict accepted physical laws, for example time travel, wormholes, or faster-than-light travel or communication.
New and different political or social systems, e.g. dystopian, post-scarcity, or post-apocalyptic .
Paranormal abilities such as mind control, telepathy, telekinesis, and teleportation .
Other universes or dimensions and travel between them.
The good side of sci-fi is that it initiates innovation and new
technology despite criticizing developing and future technologies and it sure gives back to science by broadening imagination.