atom vs isotope

atom and isotope both are nouns.

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

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

atom: (physics and chemistry) the smallest component of an element having the chemical properties of the element
isotope: one of two or more atoms with the same atomic number but with different numbers of neutrons

Other hyponyms of atom include monad, carbon atom, hydrogen atom, free radical, radical.

atom (noun)	isotope (noun)
(physics and chemistry) the smallest component of an element having the chemical properties of the element	one of two or more atoms with the same atomic number but with different numbers of neutrons
(nontechnical usage) a tiny piece of anything