The rigor and intensity of investigation on Japanese in modern linguistics has been particularly noteworthy over the past 50 years. Not only has the elucidation of the similarities to and differences from other languages properly placed Japanese on the typological map, but Japanese has served as a critical testing area for a wide variety of theoretical approaches.
Within the sub-fields of Japanese phonetics and phonology, there has been much focus on the role of mora. The mora constitutes an important timing unit that has broad implications for analysis of the phonetic and phonological system of Japanese. Relatedly, Japanese possesses a pitch-accent system, which places Japanese in a typologically distinct group arguably different from stress languages, like English, and tone languages, like Chinese. A further area of intense investigation is that of loanword phonology, illuminating the way in which segmental and suprasegmental adaptations are processed and at the same time revealing the fundamental nature of the sound system intrinsic to Japanese.
In morphology, a major focus has been on compounds, which are ubiquitously found in Japanese. Their detailed description has spurred in-depth discussion regarding morphophonological (e.g., Rendaku—sequential voicing) and morphosyntactic (e.g., argument structure) phenomena that have crucial consequences for morphological theory. Rendaku is governed by layers of constraints that range from segmental and prosodic phonology to structural properties of compounds, and serves as a representative example in demonstrating the intricate interaction of the different grammatical aspects of the language. In syntax, the scrambling phenomenon, allowing for the relatively flexible permutation of constituents, has been argued to instantiate a movement operation and has been instrumental in arguing for a configurational approach to Japanese. Japanese passives and causatives, which are formed through agglutinative morphology, each exhibit different types: direct vs. indirect passives and lexical vs. syntactic causatives. Their syntactic and semantic properties have posed challenges to and motivations for a variety of approaches to these well-studied constructions in the world’s languages.
Taken together, the empirical analyses of Japanese and their theoretical and conceptual implications have made a tremendous contribution to linguistic research.