atom vs grinding

atom and grinding both are nouns.

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

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

Other hyponyms of atom include grain, chylomicron, flyspeck, identification particle.

atom (noun)	grinding (noun)
(physics and chemistry) the smallest component of an element having the chemical properties of the element	a harsh and strident sound (as of the grinding of gears)
(nontechnical usage) a tiny piece of anything	material resulting from the process of grinding
	the wearing down of rock particles by friction due to water or wind or ice