Abstract
Some sub-dialects of the Northern Ryukyuan Dialect of Japanese keep the voiceless bilabial stop /p/ of ancient Japanese, while in some of its sub-dialects, the stop has changed to /h/, as seen in present-day Japanese dialects on the mainland of Japan. Moreover, in some Northern Ryukyuan dialects, /k/ has historically changed to /h/, and /t/ has also changed to /s/ or /θ/. These cases of spirantization of voiceless stops are all mutually related. These changes are also connected to vowel raising (o > u, e > i) and laryngealization of consonants, both of which have taken place in the Northern Ryukyuan Dialect. The degree of spirantization differs from one sub-dialect to another.
