This study aims to conduct a corpus-based register analysis of the Japanese language, targeting a wide range of registers from everyday language use to specialized domains. Utilizing multiple corpora, including the Balanced Corpus of Contemporary Written Japanese (BCCWJ) and the Corpus of Spontaneous Japanese (CSJ), the research compares the sequential patterns of conjunctions across different corpora and registers. Employing several statistical methods such as correspondence analysis, cluster analysis, and random forests, the study identifies linguistic features that distinguish written and spoken Japanese across various registers. The findings reveal significant differences in usage between written and spoken language, as well as variation between monologue and dialogue data.

This study analyzed 50 manzai routines from the 2015–2019 M-1 Grand Prix to identify structural patterns associated with higher audience evaluations. Transcripts were segmented into functional units, and sequential patterns were compared using length-normalized N-gram frequencies. High-rated routines more often resolved a boke (a deliberate deviation) quickly with a subsequent tsukkomi (an explicit corrective call-out) whereas low-rated routines exhibited prolonged set-up and additive or repetitive boke. A sensitivity analysis that collapsed consecutive identical labels (run-length encoding) yielded the same qualitative result: the advantage of short cycles that insert tsukkomi promptly persisted, while differences attributable to long identical runs diminished. These findings indicate that maintaining a short lag from boke to tsukkomi, and avoiding extended stretches of set-up or repeated boke, characterizes routines that receive higher evaluations.

This study examines 15 topics included in the Japanese Topic-Oriented Conversation Corpus (J-TOCC) by applying two classical stylistic quantitative indicators—parts of speech composition and word type composition—to the context of “topics,” and investigates their correspondences through correspondence analysis. The results show that in topics such as “03 Travel” and “07 School,” which involve recounting experiences, conversations tend to develop from concrete spatiotemporal points, resulting in frequent use of nouns. In contrast, in more social and abstract topics like “12 Dreams and Future Plans” and “13 Manners,” discourse progresses from the perspective of actions, making verbs more central. Furthermore, in topics based on subjective impressions, such as “10 Animals” and “01 Eating,” discourse was observed to develop from adjectives. From the perspective of word types, topics involving new concepts or elements of foreign origin, such as “08 Smartphones” and “04 Sports,” featured more loanwords; social and abstract topics like “12 Dreams and Future Plans” and “15 Japan’s Future” tended to favor Sino-Japanese words; and everyday life topics such as “01 Eating” and “06 Housework” showed a relative dominance of native Japanese words.

This study investigates the factors affecting the choice between the Japanese causal connectives kara and node, using the Corpus of Everyday Japanese Conversation (CEJC). The analysis demonstrates that the proportion of node increases as the level of formality rises, from casual conversation to meetings, and that node is more likely to occur in speech styles employing polite verb endings. Furthermore, while kara is overwhelmingly dominant in conversations with family members, node tends to be favored in interactions with colleagues, business partners, and customers, where considerations of politeness and social distance are more salient. These findings suggest that the choice between kara and node is systematically conditioned by social and situational factors such as the degree of formality and the nature of interlocutor relationships, and that node is especially preferred in contexts requiring interpersonal consideration.

This study aims to clarify the factors that hinder foreign guardians’ understanding of school printouts distributed in Japanese elementary schools. A total of 810 printouts were analyzed in terms of request expressions, vocabulary categories, and co-occurrence networks. The results revealed, first, that request expressions such as “kudasai (please)” and “onegaishimasu (we ask for your cooperation)” appeared frequently, indicating that repeated cooperation requests are made to guardians. Second, vocabulary categories such as “daily routines,” “events,” “money,” and “school supplies” reflected implicit norms related to punctuality, event participation, financial obligations, and preparation of belongings. Furthermore, the co-occurrence analysis suggested that vocabulary groups centered on words such as “school” and “time” form the basic structural foundation of school culture. These findings indicate that the “invisible rules” embedded in school printouts can become barriers to educational inclusion and highlight the potential effectiveness of AI support systems that supplement such cultural background.

MVR (Modifier Verb Ratio), an index that captures the stylistic features of texts in terms of part-of-speech composition, has not been sufficiently examined for its correspondence with specific stylistic features. This study explored the correspondence between MVR and stylistic features using school-song lyrics, which are texts with a relatively limited range of variation. Analysis of song lyrics from elementary, junior high, and high schools in Tokyo confirmed that MVR was higher in elementary schools than in junior high and high schools. However, the differences were due to slight differences in the M (Modifier) rates. At the individual text level, lyrics with a high N (Noun) rate were more likely to take a poetic form with many inversions and noun-phrase endings, whereas lyrics with a high V (Verb) rate were more likely to take a narrative form with predicate endings. The M-rate seemed to disrupt these patterns and neutralize the inclination toward one of the expressive forms. These results suggest that the parts-of-speech composition of school-song lyrics relates to the form in which the lyrics are realized.

This study investigates the use of the polite (desu/masu) form in children’s everyday conversations by employing the Corpus of Everyday Japanese Conversation for Children (CEJC-Child), currently being developed by the National Institute for Japanese Language and Linguistics. From approximately 50 hours of conversational data produced by ten target children in the CEJC-Child monitor version, utterances whose predicates were verbs or adjectives were extracted and classified according to plain vs. polite form, and the rate of polite form usage was calculated. The results showed that polite form began to be used consistently from around 2 to 2.5 years of age; however, the rate of polite form usage did not increase in proportion to age. A subsequent qualitative analysis of conversations with relatively high rates of polite form revealed two recurring patterns across multiple children: polite form was employed when speaking as someone other than one’s usual self, and when presenting information as certain and authoritative to the interlocutor.

This study investigates the functions and structures of teachers’ utterances in beginner-level Japanese language classes, based on a quantitative and qualitative analysis of 2,432 utterances. The analysis adopts the IRF (Initiation–Response–Feedback) framework and a dual categorization: classroom management and instructional content. Teacher utterances were flexibly adapted depending on question types and feedback orientation, playing vital roles in both linguistic scaffolding and relational coordination. The results show that teachers actively shift their utterance strategies to suit interactional needs, especially in balancing instructional clarity and learner engagement. By visualizing teachers’ improvisational responses and adaptive feedback, the study offers insights into how teacher talk functions as a tool not only for instruction but also for classroom dynamics. These findings suggest that teacher utterances should be analyzed as context-sensitive acts that mediate understanding and foster participation. The study also highlights the value of fine-grained utterance tagging and IRF-based discourse analysis in Japanese language teacher education. It demonstrates the potential for using real classroom data to support professional development and reflective practice, providing a foundation for future research on interactional competence and pedagogical flexibility in language classrooms.

This study analyzes textbooks as the primary medium for conveying a knowledge base in the context of compulsory education. It introduces a quantitative measure for assessing conceptual explanations and visualizes changes across grade levels. The analysis focuses on science textbooks from Grade 5 to Grade 8, examining three key elements: term types, the number of definition expressions, and the number of classification expressions. The findings reveal that elementary school textbooks devote more sentences and words per term compared to middle school textbooks. While term types were analyzed as a surface-level cue for concepts, the number of definition expressions—representing explicit conceptual explanations—did not align with term types. Elementary school textbooks demonstrated a significantly lower proportion of explicitly defined terms compared to middle school textbooks. Furthermore, the number of definition and classification expressions, which provide explicit conceptual explanations, increased approximately fourfold from Grade 6 to Grade 7. The study contributes to quantitative linguistic research on educational texts and offers a foundation for evaluating the clarity and accessibility of conceptual explanations in school curricula.