Genres
Space opera
Adventure SF at galactic scale: essentially fantasy in SF trappings, tolerating implausibility for mythic sweep.
Space opera is adventure science fiction set in a spacefaring civilization: essentially fantasy in SF trappings, tolerating scientific implausibility in exchange for mythic scale. The term was coined derogatorily in 1941, echoing "horse opera" for westerns, and was reclaimed decades later.
Scale is both the appeal and the continuity burden: galactic casts, polities and histories multiply fast, and long-running series lean hard on series bibles to keep their empires straight.