Ac vs actinium

Ac and actinium both are nouns.

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

As nouns, Ac and actinium are synonyms defined as:

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

Other synonyms of Ac include atomic number 89.

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