calcium vs Ca

calcium and Ca both are nouns.

Word	Noun	Adjective	Verb	Adverb
calcium	Yes	No	No	No
Ca	Yes	No	No	No

As nouns, calcium and Ca are synonyms defined as:

calcium and Ca: a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals

Other synonyms of calcium include atomic number 20.

calcium (noun)	Ca (noun)
a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals	a white metallic element that burns with a brilliant light; the fifth most abundant element in the earth's crust; an important component of most plants and animals