grind away vs bone

grind away is not a noun while bone is a noun.

Word	Noun	Adjective	Verb	Adverb
grind away	No	No	Yes	No
bone	Yes	Yes	Yes	No

As verbs, grind away and bone are synonyms defined as:

Other synonyms of grind away include bone up, cram, drum, get up, mug up, swot, swot up.

grind away (noun)	bone (noun)
	a shade of white the color of bleached bones
	rigid connective tissue that makes up the skeleton of vertebrates
	the porous calcified substance from which bones are made

grind away (adjective)	bone (adjective)
	consisting of or made up of bone

grind away (verb)	bone (verb)
study intensively, as before an exam	remove the bones from
	study intensively, as before an exam