-na

Explanation

1. -na
(formal, moderately addressee-lowering) A sentence-final ending referring to a question.

2. -na
(informal addressee-lowering) A sentence-final ending used when asking or assuming something.

Examples
요즘 일이 그렇게 많나?
장 군은 올해 졸업하나?
자네는 바둑을 둘 줄 아나?

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