Lanthanum
/ˈlænθənəm/ noun
noun ·Rare ·Advanced level
Definitions
Noun
- 1 A chemical element (symbol La) with an atomic number of 57: a soft, ductile, silvery-white metal that tarnishes slowly when exposed to air. uncountable
- 2 a white soft metallic element that tarnishes readily; occurs in rare earth minerals and is usually classified as a rare earth wordnet
- 3 An atom of this element. countable
Etymology
From Ancient Greek λανθάνω (lanthánō, “to escape notice”) + -um (“a chemical element”), because it had gone long undetected in mineral ores.