lanthanum
/ˈlænθənəm/ noun
Forms lanthanums lantanium lanthanium
- noun (uncountable) A chemical element (symbol La) with an atomic number of 57: a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air.
- noun (countable) An atom of this element.
Synonyms
Etymology
From Ancient Greek λανθάνω (lanthánō, “to escape notice”) + -um (“a chemical element”), because it had gone long undetected in mineral ores.
Webster’s 1913
- noun A rare element of the group of the earth metals, allied to aluminium. It occurs in certain rare minerals, as cerite, gadolinite, orthite, etc., and was so named from the difficulty of separating it from cerium, didymium, and other rare elements with which it is usually associated. Atomic weight 138.5. Symbol La. [Formerly written also lanthanium.]
Etymology [NL., fr. Gr. (Chem.) Defn: A rare element of the group of the earth metals, allied to aluminium. It occurs in certain rare minerals, as cerite, gadolinite, orthite, etc., and was so named from the difficulty of separating it from cerium, didymium, and other rare elements with which it is usually associated. Atomic weight 138.5. Symbol La. [Formerly written also lanthanium.]
Sources: Wiktionary · WordNet 3.0 · Webster’s 1913 — from the Wiktionary entry “lanthanum”, CC BY-SA 4.0. Details