It's not hard when we talk about an event we see in <episode A> that is revisited in <episode B>. But how about more general things, where's the dividing line with the general story background?
For example, Sisko being a single father that lost his wife is a plot continuity element that returns to play a role in several episodes throughout DS9. Yet you could also see it as part of the background story, since these events don't actually happen within the DS9 time span (though we do get to see a flashback in Emissary). But then, Jadzia being replaced by Ezri happens within the series. Could you say that most of DS9: S7 is a continuation on that?
For example, Sisko being a single father that lost his wife is a plot continuity element that returns to play a role in several episodes throughout DS9. Yet you could also see it as part of the background story, since these events don't actually happen within the DS9 time span (though we do get to see a flashback in Emissary). But then, Jadzia being replaced by Ezri happens within the series. Could you say that most of DS9: S7 is a continuation on that?
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