무슨 뜻입니까?
뭐 필요한 거 없어요? does this mean ''do you need sth?'' or don't have a need for anything? what is 없어요 purpose here? 뭐 필요한 거 없어요? and 뭐 필요한 거 있어요? are these both correct??

Question

무슨 뜻입니까?
뭐 필요한 거 없어요? does this mean ''do you need sth?'' or don't have a need for anything?  what is 없어요 purpose here? 뭐 필요한 거 없어요? and 뭐 필요한 거 있어요? are these both correct??

Answer

They are all correct sentence, and can be replaced with each other. However, the nuances of their meanings are slightly different.

뭐, 필요한 거 있어요? (O)
Well, Is there anything you need?
or
Well, Do you need anything (more)?

뭐, 필요한 거 없어요? (O)
Well, Don't you need anything (more)?
or 
Are you satisfied? or Is that enough?

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