friction vs grinding

friction and grinding both are nouns.

Word	Noun	Adjective	Verb	Adverb
friction	Yes	No	No	No
grinding	Yes	No	No	No

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

friction: the resistance encountered when one body is moved in contact with another
grinding: the wearing down of rock particles by friction due to water or wind or ice

Other hyponyms of friction include abrasion, attrition, detrition, adhesive friction, grip, traction.

friction (noun)	grinding (noun)
effort expended in moving one object over another with pressure	a harsh and strident sound (as of the grinding of gears)
the resistance encountered when one body is moved in contact with another	material resulting from the process of grinding
a state of conflict between persons	the wearing down of rock particles by friction due to water or wind or ice