1. a yellow trivalent metallic element of the rare earth group; occurs in monazite and bastnasite in association with cerium and lanthanum and praseodymium
2. An elementary substance which forms one of the constituents of didymium. Symbol Nd. Atomic weight 140.8.
3. 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.