calculus vs nephrolith

calculus and nephrolith both are nouns.

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

As nouns, nephrolith is a hyponym of calculus; that is, nephrolith is a word with a more specific, narrower meaning than calculus:

calculus: a hard lump produced by the concretion of mineral salts; found in hollow organs or ducts of the body
nephrolith: a calculus formed in the kidney

calculus (noun)	nephrolith (noun)
the branch of mathematics that is concerned with limits and with the differentiation and integration of functions	a calculus formed in the kidney
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