a trivalent metallic element of the rare earth group; occurs with yttrium
A chemical element (symbol Er) with atomic number 68: a silvery-white metal, in nature always found in combination with other elements.
The name erbium comes from New Latin, derived from the Swedish town of Ytterby where the element was first discovered. Swedish chemist Carl Gustaf Mosander coined the term in 1843 by adding the suffix -ium to the town's name.