From WordNet (r) 3.0 (2006): atomic number 68 n 1: a trivalent metallic element of the rare earth group; occurs with yttrium [syn: erbium, Er, atomic number 68]
atomic number 68 n 1: a trivalent metallic element of the rare earth group; occurs with yttrium [syn: erbium, Er, atomic number 68]
