Vo or vos?

[ValekLost]

While I was reading the episodes scripts, I saw:

"Rakharo: Vo mawizzi vekho jinne -There are no rabbits. "
"Rakharo: Dothraki vo ondeo shori tawakof. - Dothraki don't wear steel dresses. "
"Rakharo: Hash yer ray tih loy alegra zhey vikeesi? Vo mawizzi, vo alegri."
"Drogo: Vo sorfo. Rhaeshi. - Not dirt. Lands"

and some more

But in the dictionnary I found only "vos" as "not".

Why in some sentences there is "vo" and in others "vos" ?
I was wondering it was for the future tense, but that's not true 

I didn't find anything in the wiki, but I don't know if I missed that or if there isn't nothing at all.   

[ingsve]

Ya, that's something that was clarified by David just recently. Basically vo and vos are interchangeable. Vos is the standard but in cases where the following words starts with a consonant it's also possible to use vo instead to help pronounciation. That doesn't explain the instances where vo is seen ahead of a vowel but that can probably be explained by mistakes.

[ValekLost]

Ah good.
Firstly I thought about consonant/vowel case too, but like you said "vo" there is in both cases, so I discard it immediately, but if the "vo" ahead of a vowel could be considered a mistake, so...it makes sense

By the way, it's:

if the word that follow the negation starts with a consonant, it could be used "vo" instead of "vos" to help the pronunciation but it's optional, while it would be an error to use "vo" ahead of a vowel.

Right?

[ingsve]

Ah good.
Firstly I thought about consonant/vowel case too, but like you said "vo" there is in both cases, so I discard it immediately, but if the "vo" ahead of a vowel could be considered a mistake, so...it makes sense

By the way, it's:

if the word that follow the negation starts with a consonant, it could be used "vo" instead of "vos" to help the pronunciation but it's optional, while it would be an error to use "vo" ahead of a vowel.

Right?

Yes, that's right.