ナトリウム

1807 is the key date for sodium: Humphry Davy isolated the element from caustic soda, and German Natrium names the same element with symbol Na. Duden lists Natrium as a neuter German noun and connects it with Natron; PubChem says Na comes from Latin natrium for natron. Japanese ナトリウム copies the German form, not English sodium. In Meiji chemistry, German-style element names sat beside school and medical terms such as カリウム, マグネシウム, and アルミニウム. Kotobank's Digital Daijisen labels ナトリウム as German Natrium and gives sodium as the English equivalent. The meaning changed little: it stayed an element name, then entered compound names such as 塩化ナトリウム for NaCl and 炭酸ナトリウム for Na2CO3. Today ナトリウム appears in chemistry class, medicine, and food labels, often with 食塩相当量 in nutrition tables. Atomic number 11 remains the same in both languages. The main difference from English is the basic name: English uses sodium, while Japanese uses ナトリウム, with ソジウム listed only as a secondary form in some dictionaries. Example: 食品表示に「ナトリウム 400 mg」とある.