"What?"

[Kì'eyawn]

Kaltxì ma eylan.  So, in English when someone doesn't understand and/or believe what you've said, you'll get the response,

"What?"

But of course, Na'vi makes this a little more complicated.  My instinct is that the Na'vi might do something like this:

If the Na'vi don't understand you correctly, i'd expect they would say, 'upe?  As in, 'Upe nga pìlmtxe?

Whereas if the "what" refers to part of what you said, you might get specificity that English lacks.  Take a look at this:

Suppose one Na'vi says, Tspolang Tsu'teyl Sawtutet.  If a second Na'vi asks, Kempe?, we know he means, Kempe Tsu'tey soli?; whereas if the second Na'vi asks, 'Upe?, we know he means, 'Upe Tsu'teyl tspolang?.  Does that seem right to you, ma smuktu?

P. S. Do we know yet if question words can take case markers (e.g., would it be *Peut Tsu'teyl tspolang)?  I've never seen it...

[Kemaweyan]

Yeah, I often use "peu?" for re-ask when I don't understand But I never think that is part of  question "Peu nga pìlmlltxe?", I use it only as interjection with meaning "I don't understand what did you say"...

And if you want to ask "What did you just say?", you must use ergative and accusative cases: "Peut ngal pìlmlltxe?", therefore short question should be "Peut?" or "'Upet?" But I don't know, is the verb "plltxe" transitive or not. Maybe better to use the verb "peng"? Or if "plltxe" is not transitive, it shoul be "Peuteri nga pìlmlltxe?"..

[kewnya txamew'itan]

plltxe is indeed intransitive, and peu nga pìmlltxe makes little sense, which is speaking, nga or peu? Really it would be short for "nga pìmlltxe san peu".

That said, I think, like kemaweyan that it's obvious where it's come from, it is  probably more of an interjection in its own right now.

Lastly, I think it should probably be inflected for case as normal, so when asking what Tsu'Tey killed, I'd say peut or 'upet.

[MIPP]

Hum... I don't know... I truly believe that there is some idiomatic expression that we don't know yet... or maybe not 

[Kemaweyan]

plltxe is indeed intransitive, and peu nga pìmlltxe makes little sense, which is speaking, nga or peu? Really it would be short for "nga pìmlltxe san peu".

Irayo nìtxan

Lastly, I think it should probably be inflected for case as normal, so when asking what Tsu'Tey killed, I'd say peut or 'upet.

Yeah, but I can ask this only if I understood least part of speech. But if I did not hear whole phrase, I ask just "peu?"

[Sireayä mokri]

May be it's better to use "lì'upe" in "what did you just say"?

[Kì'eyawn]

Lastly, I think it should probably be inflected for case as normal, so when asking what Tsu'Tey killed, I'd say peut or 'upet.

So, have we had that confirmed?  The question words do inflect for case?

[Kemaweyan]

Lastly, I think it should probably be inflected for case as normal, so when asking what Tsu'Tey killed, I'd say peut or 'upet.

So, have we had that confirmed?  The question words do inflect for case?

I think it's obvious Without cases meaning can be not clear. But I can't remember Paul used this words or not...

[kewnya txamew'itan]

Lastly, I think it should probably be inflected for case as normal, so when asking what Tsu'Tey killed, I'd say peut or 'upet.

So, have we had that confirmed?  The question words do inflect for case?

I don't think so. It just strikes me as a natural application of the case system. As Kemaweyan rightly pointed out though, if you don't know what argument the word you didn't hear was, you couldn't do that.

May be it's better to use "lì'upe" in "what did you just say"?

This seems nicer to me than 'upe actually.

[Kì'eyawn]

I think it's obvious Without cases meaning can be not clear. But I can't remember Paul used this words or not...

Furia fì'uluke ral ke lu law mllte oe ngahu, ma Kemaweyan.  Slä oel ke tsole'änga tsat kawkrr...
I agree with you that without this the meaning is not clear, Kemaweyan.  But i have never seen it...

[Kemaweyan]

Furia fì'uluke ral ke lu law mllte oe ngahu, ma Kemaweyan.  Slä oel ke tsole'änga tsat kawkrr...
I agree with you that without this the meaning is not clear, Kemaweyan.  But i have never seen it...

Kxawm ke lamu tìkin
Maybe was no need

May be it's better to use "lì'upe" in "what did you just say"?

This seems nicer to me than 'upe actually.

Then maybe better "aylì'upe"? Phrases usually consist of several words

[Sireayä mokri]

I think it's obvious Without cases meaning can be not clear. But I can't remember Paul used this words or not...

I agree as well. I always see peu as 'u with marker. Therefore we still need to use case on 'u.

Then maybe better "aylì'upe"? Phrases usually consist of several words

Sure. But "what did you just say" not always refers to a phrase.

[omängum fra'uti]

When I'm using Na'vi in conversations and I hear only part of what was said, I try to repeat what I did hear, then throw a question word in for the part I didn't.  It also helps make sure you heard the rest right, because if you repeat it wrong they can correct it.

[MIPP]

When I'm using Na'vi in conversations and I hear only part of what was said, I try to repeat what I did hear, then throw a question word in for the part I didn't.  It also helps make sure you heard the rest right, because if you repeat it wrong they can correct it.

And repeating, you also memorize some words and improve your pronounciation.

[burritoninja007]

Alternatively, perhaps it's possible that there isn't a word for it.  The Na'vi's facial and body language are more integrated than ours and all of their communicating is done face to face.  Perhaps their version could be a puzzled look or twitching of the ears.  The closest example I could find in the movie was when Jake Sully was confessing his true mission and Neytiri responded in English "what are you saying, Jake?" though it was more for clarification rather than repetition.  Just a thought 

[Plumps]

Confirmation on case endings on question words in an interview here. Payoang translated and that can be found somewhere in the News section.