カルシウム

1808 is the chemical date behind calcium: Humphry Davy isolated metallic calcium with help from J. J. Berzelius and M. M. af Pontin. The word calcium is New Latin, from Latin calx, calcis, meaning lime or limestone. PubChem and Britannica both give Ca as the symbol and atomic number 20. Japanese カルシウム reflects the international scientific form calcium. In Japan, the printed record is clearly Meiji: Kotobank's Seisenban Nihon Kokugo Daijiten cites 文部省 小学化学書, 1874, with カルシユム. Unlike ナトリウム and カリウム, the form is close to English, Dutch, and older European chemistry spellings. It entered the field of school chemistry with related words such as 石灰, 炭酸カルシウム, and 塩化カルシウム. Today カルシウム is both an element name and a nutrition word on milk, small-fish snacks, supplements, and bone-health articles. English calcium covers the element and the nutrient too, so the difference is smaller than with sodium and potassium. Japanese, however, often uses カルシウム不足 as a daily health phrase. Example: 牛乳でカルシウムをとる.