callus vs scar

callus and scar both are nouns.

Word	Noun	Adjective	Verb	Adverb
callus	Yes	No	Yes	No
scar	Yes	No	Yes	No

As nouns, scar is a hypernym of callus; that is, scar is a word with a broader meaning than callus:

Other hypernyms of callus include cicatrice, cicatrix.

callus (noun)	scar (noun)
(botany) an isolated thickening of tissue, especially a stiff protuberance on the lip of an orchid	an indication of damage
bony tissue formed during the healing of a fractured bone	a mark left (usually on the skin) by the healing of injured tissue
an area of skin that is thick or hard from continual pressure or friction (as the sole of the foot)

callus (verb)	scar (verb)
form a callus or calluses	mark with a scar
cause a callus to form on