What is the difference between science fiction and fantasy?

i love science fiction and fantasy, but i just recently started wondering about what the difference between the two really is. sometimes it might be obvious, like how the lord of the rings is obviously fantasy, but there are other times where it seems a little questionable to me... star wars, for example, seems... show more i love science fiction and fantasy, but i just recently started wondering about what the difference between the two really is. sometimes it might be obvious, like how the lord of the rings is obviously fantasy, but there are other times where it seems a little questionable to me... star wars, for example, seems like it could be categorized as either science fiction or fantasy.
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