What are the distinguishing features of a story that cause it to be considered science fiction?

Answer 1

Here are some elements that make a story Science Fiction:

• Time: story is set in the future, an alternate timeline, or an alternate history
• Space: story is set on another planet, in another dimension, in outer space, or somewhere else that is possible, such as underneath the planet's surface or underwater
• Characters: story includes characters such as robots, aliens, mutants, or cybernetic humans
• Technology: story includes technology beyond what we have today, such as wrap drives, plasma weapons, teleportation devices, or human-computer interfaces.
• Science: story includes science that is beyond what we know today, or that contradicts what we know today
• Social: story included political, cultural, or social situations which would create or sustain any of the above (such as post-apocalypse, dystopias, or utopias)
• Paranormal: story includes super-human abilities such as telepathy, telekinesis, or mind control.

Here is a link to the entire WikiPedia article about the elements of science fiction.

Answer 2

Science fiction must contain plausible science, even if it is set in the future or an alternate universe. It must also be a work of fiction, which is to say, a made-up story.