Science fiction - and the correct shortcut is 'sf' - uses actual scientific facts or theories for the source ideas or framework of the story. It has some scientific content, however speculative. If it breaks a law of physics, it knows it's doing so and follows up the consequences. If it invents a society of aliens, it does so with some respect for and knowledge of the social sciences and what you might call social probabilities. And some of it is literarily self-aware enough to treat its metaphors as metaphors.

Oh, never and forever aren't for mortals, love. But we won't be parted till I know it's right that we part.

There is no kingdom like the forests.

I write with all my heart

But it doesn't take a thousand men to open a door, my lord." "It might to keep it open.

The law of evolution is that the strongest survives.

Why can I never set my heart on a possible thing?