This is the 99th most frequent Swedish word.
fall
"Fall" in Swedish means "case," "fall," or "incident," depending on the context.
Here, 'fall' refers to a 'case' or 'situation'.
I det här fallet har du rätt.
In this case, you are correct.
In this context, 'faller' is the verb form of 'fall' meaning 'to decline' or 'to drop'.
Om du inte tränar, faller din kondition.
If you don't exercise, your fitness will decline.
'Fall' here is part of the compound word 'vattenfall', meaning 'waterfall'.