Lu vs lutetium

Lu and lutetium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Lu	Yes	No	No	No
lutetium	Yes	No	No	No

As nouns, Lu and lutetium are synonyms defined as:

Lu and lutetium: a trivalent metallic element of the rare earth group; usually occurs in association with yttrium

Other synonyms of Lu include atomic number 71, lutecium.

Lu (noun)	lutetium (noun)
a trivalent metallic element of the rare earth group; usually occurs in association with yttrium	a trivalent metallic element of the rare earth group; usually occurs in association with yttrium