attrition vs eating away

attrition and eating away both are nouns.

Word	Noun	Adjective	Verb	Adverb
attrition	Yes	No	No	No
eating away	Yes	No	No	No

As nouns, eating away is a hypernym of attrition; that is, eating away is a word with a broader meaning than attrition:

attrition: erosion by friction
eating away: (geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively

Other hypernyms of attrition include eroding, erosion, wearing, wearing away.

attrition (noun)	eating away (noun)
the act of rubbing together; wearing something down by friction	(geology) the mechanical process of wearing or grinding something down (as by particles washing over it), also figuratively
a wearing down to weaken or destroy
sorrow for sin arising from fear of damnation
the wearing down of rock particles by friction due to water or wind or ice
erosion by friction