  We introduce a Japanese Morphology dataset, J-UniMorph, developed based on
the UniMorph feature schema. This dataset addresses the unique and rich verb
forms characteristic of the language's agglutinative nature. J-UniMorph
distinguishes itself from the existing Japanese subset of UniMorph, which is
automatically extracted from Wiktionary. On average, the Wiktionary Edition
features around 12 inflected forms for each word and is primarily dominated by
denominal verbs (i.e., [noun] +suru (do-PRS)). Morphologically, this form is
equivalent to the verb suru (do). In contrast, J-UniMorph explores a much
broader and more frequently used range of verb forms, offering 118 inflected
forms for each word on average. It includes honorifics, a range of politeness
levels, and other linguistic nuances, emphasizing the distinctive
characteristics of the Japanese language. This paper presents detailed
statistics and characteristics of J-UniMorph, comparing it with the Wiktionary
Edition. We release J-UniMorph and its interactive visualizer publicly
available, aiming to support cross-linguistic research and various
applications.
