The Difference: Sake vs. Nihonshu vs. Seishu
Sake is an alcoholic beverage of Japanese origin made by fermenting non-glutinous rice called “Sakamai (酒米)” that is suitable for brewing sake.
Sake is represented as “酒” using kanji or a Chinese character, which, in a broad sense, can refer to any kind of alcoholic drink.
Sake vs. Nihonshu vs. Seishu
Sake, known as Japanese rice wine in a narrow sense, is referred to as “Nihonshu (日本酒)” in Japan.
It is a “Seishu (清酒)”, but how do Nihonshu and Seishu differ?
Seishu is sake whose main ingredients are rice, malted rice (kome-koji), and water, which may (can) be produced outside of Japan.
Nihonshu is Japanese sake. The main ingredients are rice, malted rice, and water, the same as Seishu.
But unlike Seishu, Nihonshu only uses (must use) domestic rice and is (must be) produced in Japan.
(Reference Pages: nta.go.jp, magazine.asahi-shuzo )