Neodymium

1. (n.) An elementary substance which forms one of the constituents of didymium. Symbol Nd. Atomic weight 140.8.
2. (n.) A rare metallic element occurring in combination with cerium, lanthanum, and other rare metals, and forming amethyst-colored salts. It was separated in 1885 by von Welsbach from praseodymium, the two having previously been regarded as a single element (didymium). It is chiefly trivalent. Symbol Nd; at. wt. 144.3.