Proto-Japonic; Proto-Japanese-Ryukyuan
Technical term in historical linguistics referring to the reconstructed common ancestor of Japanese and the Ryukyuan languages.
Research on Proto-Japonic clarifies the genetic relationship between Japanese and the Ryukyuan languages.
A general term for 'proto-language'; 日琉祖語 specifically refers to the proto-language of the Japonic family.
Proto-Ryukyuan, the reconstructed ancestor of the Ryukyuan languages, which is a descendant of 日琉祖語.
Compound of 日 (にち, 'Japan'), 琉 (りゅう, 'Ryukyu'), and 祖語 (そご, 'proto-language'). The term was coined in modern Japanese linguistics.