Polite for 元気がないな

[Yuta73]

This is apparently a trivial phrase, but I have problems parsing its parts. Maybe seeing how's the polite version might help. I have several questions also.
What's the implied verb?, いる、です
Why the な at the end. He's no issuing an order.
Can じゃない be used in this kind of sentence?

 

[Angel Valis]

The polite version would simply be 元気がありませんな.

The verb in this case is ある, ない is the plain form of the non-past negative ありません.

な at the end of a sentence is an introspective particle, it's used when you're talking to yourself. Sort of like "Not looking well, huh?". But unlike ね which is sometimes translated as "huh?" or "right?", な doesn't actually seek agreement with others, and rather indicates a comment to one's self.

じゃない can not be used here because じゃない is the plain form of じゃありません which is used to negate nouns and as the negative endings of な adjectives.

 

[Toritoribe]

Actually, the polite version is 元気がありませんね. 元気がありませんな is used only by old people(male).
元気がないな can be used also for others in the similar meaning to (but with a more indirect nuance than) 元気がないね. So the meaning (talking to others or the speaker's self) depends on the context.

Can じゃない be used in this kind of sentence?

元気がない means "depressed", whereas 元気じゃない often connotes "sick".

 

[Angel Valis]

Thanks for the clarification. I wasn't aware of that usage of な.

Also I learned 元気がない to simply mean that someone doesn't look well (used in the context of being sick-looking). And I suppose I should have clarified the 元気じゃない point. Thank you for catching my inexperienced response.

 

[Yuta73]

二人共、ありがとうございます。
先生と弟子は話してでした。(I just hope that I wrote it well)

I can see now, vｅｒy clarifying explanations. Angel Valis's one fits perfectly the context, as the student was indeed sick. And also the sensei is actually old.

So, ある can be used on people also, uh?.

 

[Toritoribe]

I said just about ～ますな/ませんな/ですな or "the polite form + な". ～ないな can be used also by young people.