나

wondering "is it…?"; guessing

Ends a clause with an open, unsure question the speaker is turning over: 맞나 is "is that even right?", 누가 말했나? is "who said that?". Its most common use here is inside two set phrases — -나 보다, which guesses from evidence (교통이 안 좋았나 봐요, "traffic must have been bad"), and -지 않나 / -지 않았나 싶다, which floats an opinion gently (그렇지 않나, "isn't that so?"). All of these soften a claim rather than assert it. One example, 중요하나 건강이 최고다, uses an older written form meaning "though", which you will mostly meet in proverbs and slogans rather than speech.

Register: musing, softening