In Okinawan, there are multiple possible ways to mark a question. One key difference appears to be a distinction between polar (or yes-no) questions and content (or wh-) questions. Polar questions are marked by the verbal enclitic =i, while content questions are marked with the phrasal enclitic =ga. For instance, compare the following pair of sentences:
(1) maa=nkai ʔich-abii=ga
‘Where are you going?’
(2) Naafa=nkai ʔich-abii-m=i
‘Will you go to Naha?’
However, unlike its cognate in modern Japanese, =ka, Okinawan =ga can also appear next to the phrase which it has scope over, not just the entire sentence. This in some ways resembles quantifier float. For instance:
(3) kunu yama=nu ʔuchee shichina-ʔudun=ga ya-yabii-ra
this forest=GEN inside\TOP Shichina-Udun=CQ COP-POL-TENT
‘Is Shichina Udun inside this forest?’ (Nakamatsu 1973: 78)
This is interesting in two ways.
First, the distinct between polar and content questions is lost. (3) is quite clearly a polar question, yet it does not use the polar question enclitic =i. Instead, it has the content question enclitic =ga. As far as I know, the enclitic =i is a verbal enclitic; that is, it can only attach to verb phrases. The enclitic =ga, on the other hand, can attach to a variety of different elements. At the least noun phrases, case phrases, and the infinitive form of verbs.
Second, there is a difference in the modal forms used in the sentences. There are a number of processes in Japonic languages, in the Japanese literature called kakari musubi (係り結び), where certain kinds of focus particles (including question particles) alter the mood of the main verb of the sentence. In (1), there is no mood suffix with =ga. However, with =i, as in (2), the final form -n ~ -m- (which marks the verb as being the matrix predicate of a sentence) is obligatory. Curiously, in (3)—and other cases where the content question clitic “floats”, the tentative mood marker -(u)ra is required.
I’m not really satisfied with any sort of explanation for what I’ve been calling the “final” suffix in any Japonic language. I think we have pretty good evidence that something mood-related is going on, as it is fairly clearly from all other cases of these sorts of kakari musubi phenomenon, in whatever variety of Japonic you want to look at, aside from this final suffix and another suffix called the attributive (which marks the verb phrase as being the modifier in a relative clause, as in (4a) and (b)), these are modal markers that are involved. However, what sort of mood we’re dealing with in terms of the final and the attributive I don’t think is very clear at this point.
(4a.) sumuchi yum-u-n
‘I read a book.’
(4b.) yum-uru sumuchi
‘the book that I read’
Nakamatsu, Takeo. 1973. Okinawago no Bunpō [Okinawan Grammar]. Naha: Okinawa Hōgen Bunka Kenkyū-zyo.