The following list presents most of the historical sound changes that have affected Central Okinawan, in relation to Classical Japanese and more or less to modern Japanese. The sound changes are presented by general order of progression, so by following the changes from top to bottom, you should be able to derive most words if you know their Japanese counterparts.

Note that the following list uses the International Phonetic Alphabet , and that the capital letter /C/ represents any given consonant, /V/ a vowel, and /N/ represents Okinawan's moraic nasal. Some examples will be provided in the following post.

Sound Changes

Long vowels coalesce:
/au/, /ao/ → /oo/
/ai/, /ae/ → /ee/
/ei/ → /ii/
/e(ɸ)u/ → /uu/

Yotsugana merge:
/tu/ → /ti/ → /t͡ɕi/
/su/ → /si/ [ɕi]
/zu/ → /zi/ → /d͡ʑi/
/du/ → /di/ → /d͡ʑi/

T and K palatalize to CH, and D and G palatalize to J:
/ti/, /ki/ → /t͡ɕi/
/di/, /gi/ → /d͡ʑi/
/t(i)j/, /k(i)j/ → /t͡ɕ/
/d(i)j/, /g(i)j/ → /d͡ʑ/

Nasal assimilation:
/Nd/ → /d/

Moraic:
The sequences /nu/, /ni/, /mu/ and /mi/ reduce to the moraic nasal /N/.
(Exception: /mu/ does not appear to reduce before /r/ in word-initial position only)

Flap:
/ɾi/ → /i/ (some exceptions exist, e.g. the sequence /iɾi/ remains unchanged)

Short mid vowels are raised:
/e/ → /i/
/o/ → /u/

Note: Palatalization among other changes precedes short mid vowel raising, so:

• /ke/ becomes /ki/ [ki], and /te/ becomes /ti/ [ti] (not /t͡ɕi)
• /ge/ becomes /gi/ [gi], and /de/ becomes /di/ [di] (not /d͡ʑi)
• /ɾe/ becomes /ɾi/ (not /i/)
• /no/ becomes /nu/ (not /N/), etc.

However: /se/ exceptionally becomes /si/ [ɕi] (no difference)

Other changes:
/awa/ → /aa/ (except if followed by another vowel)
/z/ → /d͡ʑ/
/Nɾ/ → /Nd/
/aN/ → /a/ (at the end of a word)

Short vowels in monomoraic words lengthen:
/CV/ → /CVV/

Historically palatalized sequences with /j/ will depalatalize:
/s(i)j/ → /s/
/z(i)j/ → /d͡ʑ/
/m(i)j/ → /n/

All word-initial vowels predictably glottalize:
/V..../ → [ʔV....] (arguably /ʔ...../)

Preglottalization of word-initial vowels also led to the following changes:
/uwV/ → /ʔwV/
/unV/ → /ʔNnV/
/umV/ → /ʔNmV/
/ijV/ → /ʔjV/

Note: Other changes and differences do exist, but they are not always predictable. For example, the long vowel /oo/ (stemming from the historical sequence /au/ or /ao/) sometimes raises to /uu/. Central Okinawan also features sporadic vowel lengthening of the first or second syllable of a disyllabic word, retains the historical sound /ɸ/ in some words but not others, has different vowel coalescence rules for topicalization, etc. Some differences may also exist between Okinawan and Japanese because the historical forms were simply different.

Here are some example vocabulary to demonstrate the previous changes:

/okinawa/ "Okinawa"
> /ot͡ɕinawa/ (palatalization)
> /ut͡ɕinawa/ (short mid vowel raising)
> /ut͡ɕinaa/ (intervocalic -w- dropping)
= [ʔut͡ɕinaa] (word-initial vowel glottalization)

/toɾi/ "bird"
> /tuɾi/ (short mid vowel raising)
> /tui/ (ɾi to i reduction)
= [tui]

/mune/ "chest"
> /Nne/ (mu to N)
> /Nni/ (short mid vowel raising)
= [n̩ni]

/ame/ "rain"
> /ami/ (short mid vowel raising)
= [ʔami] (word-initial vowel glottalization)

*/s(i)joɾi/ "Shuri (the capital of Okinawa)"
> /sjuɾi/ (short mid vowel raising)
> /sjui/ (ɾi to i)
> /sui/ (depalatalization)
= [sui]

*/ijo/ "fish"
> /iju/ (short mid vowel raising)
> [ʔiju] (preglottalization)
> /ʔju/ (glottalized vowel assimilated into glide)
> /ʔjuu/ (monomoraic word vowel lengthening)
= [ʔjuu]

*/sataN/ "sugar"
> /sata/ (-aN to -a)
> /saataa/ (sporadic vowel lengthening)
> [saataa]

*/komuɾa/ "leg; calf of the leg"
> /koNɾa/ (mu to N)
> /kuNɾa/ (short mid vowel raising)
> /kuNda/ (Nɾ to Nd fortition)
= [kun̩da]

*/sekai/ "world"
> /sekee/ (ai to ee)
> /sikee/ (short mid vowel raising)
= [ɕikee]