calculate vs calculus

calculate is not a noun while calculus is a noun.

Word	Noun	Adjective	Verb	Adverb
calculate	No	No	Yes	No
calculus	Yes	No	No	No

calculate (noun)	calculus (noun)
	the branch of mathematics that is concerned with limits and with the differentiation and integration of functions
	a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body
	an incrustation that forms on the teeth and gums

calculate (verb)	calculus (verb)
make a mathematical calculation or computation
specifically design a product, event, or activity for a certain public
judge to be probable
have faith or confidence in
predict in advance
keep an account of