erbium vs Er

erbium and Er both are nouns.

Word	Noun	Adjective	Verb	Adverb
erbium	Yes	No	No	No
Er	Yes	No	No	No

As nouns, erbium and Er are synonyms defined as:

erbium and Er: a trivalent metallic element of the rare earth group; occurs with yttrium

Other synonyms of erbium include atomic number 68.

erbium (noun)	Er (noun)
a trivalent metallic element of the rare earth group; occurs with yttrium	a trivalent metallic element of the rare earth group; occurs with yttrium