What does the ending 구만 mean and how do you use it?

Question

Answer

Sometimes it shows an unexpected fact.
Ex: 한국말 아주 잘 하는구만
(translation) You speak Korean very well. (Actually I doubted you can do that)

Answer

When you use 구만 it sounds like you're talking to yourself.

Answer

~구만 is a wrong form of ~구먼

~구먼 has same meaning and usage with ~구나
Both forms are often said when one realizes a new fact or piece of information.

The difference is in speech levels.

~구먼 is Hage-che(하게체)
It is used only
- by some older people when addressing younger people, friends, or in-laws in a friendly manner
- between adult male friends, occasionally
- in novels
e.g. 자네는 돈이 별로 없구먼!

~구나 is Haera-che(해라체)
It is used
- to close friends or relatives of similar age, and by adults to children
- in impersonal writing (books, newspapers, and magazines) and indirect quotations ("She said that...")
- in grammar books, to give examples
- in some exclamations
e.g. 날이 밝았구나!

Answer

Sometimes it shows an unexpected fact.
Ex: 한국말 아주 잘 하는구만
(translation) You speak Korean very well. (Actually I doubted you can do that)