actinium vs Ac

actinium and Ac both are nouns.

Word	Noun	Adjective	Verb	Adverb
actinium	Yes	No	No	No
Ac	Yes	No	No	No

As nouns, actinium and Ac are synonyms defined as:

actinium and Ac: a radioactive element of the actinide series; found in uranium ores

Other synonyms of actinium include atomic number 89.

actinium (noun)	Ac (noun)
a radioactive element of the actinide series; found in uranium ores	a radioactive element of the actinide series; found in uranium ores