Sentence-Final Morphology in Japanese and Tungusic: A Structural Parallel within the Northeast Asian Linguistic Sphere

This study examines a distinctive grammatical feature shared by Japanese and the Tungusic languages, particularly Manchu: the sentence is not closed by the finite verb form, but by an additional layer of clause-final morphology encoding modality, evidentiality, and speaker stance. In Japanese, the so-called shūshikei (“terminal form”) functions as a morphologically defined category but does not serve as the natural, unmarked sentence-final form in everyday conversation. Instead, spoken Japanese overwhelmingly relies on sentence-final particles (yo, ne, na) and extended predicate constructions (–nda, –n be, –n da be, –tto), many of which are preserved most vividly in regional dialects. Tungusic languages display an analogous structure. In Manchu, bare verb stems rarely appear sentence-final; clauses must be closed with suffixes such as –ambi or –ombi. Similar systems exist across Evenki, Nanai, Udehe, and Oroch. These parallels indicate a shared structural tendency: verbs lack inherent finite force, and the pragmatic completion of a sentence is expressed by specialized clause-final morphology. The paper argues that this feature reflects a broader Northeast Asian linguistic area (Sprachbund) including the languages of the historical Buyeo–Goguryeo sphere, Tungusic languages, and early Japanese. This has implications for the typological classification of Japanese and challenges its comparison with Indo-European or Sinitic languages, where finite verb forms naturally function as sentence-final predicates. The analysis integrates typology, dialectology, and historical linguistics to propose that Japanese preserves a deep areal connection with the grammar of Northeast Asia.