느냐 can be used in many situations but 느냐 is very iffy in Korean ex) 1) 지금 이순간을 어떻게 느끼느냐 이걸 얼마나 깊게 들여 마시느냐(?) 그런 게 더 중요하다는 거죠 (It is more important that how am i sensing of this momentum and how deep i can take it in(?)) vs 2) 지금 이순간을 어떻게 느끼는지, 이걸 얼마나 깊게 들이 마시는지, 그런것들이 더중요하다 Both are the same meaning but there's a difference in attitude I can see (1) is less formal. the speaker is trying to keep up doing speech, by using 느냐 at the end of every praises, the speaker is trying to make sure that listener to get that the speech is not done yet. (2) will work fine as much as (1). It's relatively formal I am not sure about that 느냐 is somehow related with rhetorical question. 느냐 also can be used. When a very old person ask a something to much younger person, Very rarely used. ex)지금 몇시인지 아느냐? So these 2 examples are the what i can bring up here right now. Generally people don't use 느냐 really often it's an ole term/word so you can find it very rarely in Korean