Why do historians sometimes describe East Asian mathematics as mathematics in Chinese characters?

Historians sometimes describe East Asian mathematics as "mathematics in Chinese characters" because the Chinese writing system was adopted by Japan, Korea, and Vietnam early in their histories alongside other cultural institutions.1

Because these nations shared a common writing system, mathematical texts produced in any one of these countries could circulate throughout the entire region. Scholars in Japan, Korea, and Vietnam initially learned from Chinese sources, and over time, mathematical works produced in Japan and Korea also found their way to China.1

Using the term "mathematics in Chinese characters" is considered more appropriate than "Chinese mathematics" because it acknowledges this regional exchange and the shared scholarly tradition that transcended national borders. While the mathematical tradition originated in China, the development of the field in East Asia was a collective process involving the movement of books and ideas across these neighboring cultures.12