Pm vs promethium

Pm and promethium both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pm	Yes	No	No	No
promethium	Yes	No	No	No

As nouns, Pm and promethium are synonyms defined as:

Pm and promethium: a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium

Other synonyms of Pm include atomic number 61.

Pm (noun)	promethium (noun)
a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium	a soft silvery metallic element of the rare earth group having no stable isotope; was discovered in radioactive form as a fission product of uranium