Er and Metallic element

Er noun - A trivalent metallic element of the rare earth group; occurs with yttrium.

Metallic element and er are semantically related. In some cases you can use "Metallic element" instead a noun "Er".

Metallic element noun - Any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc..

Er and metallic element are semantically related. Sometimes you can replace term "Er" with "Metallic element", this terms are similar.