iodine-131 vs radioisotope

iodine-131 and radioisotope both are nouns.

Word	Noun	Adjective	Verb	Adverb
iodine-131	Yes	No	No	No
radioisotope	Yes	No	No	No

As nouns, radioisotope is a hypernym of iodine-131; that is, radioisotope is a word with a broader meaning than iodine-131:

iodine-131: heavy radioactive isotope of iodine with a half-life of 8 days; used in a sodium salt to diagnose thyroid disease and to treat goiter
radioisotope: a radioactive isotope of an element; produced either naturally or artificially

Other hypernyms of iodine-131 include atomic number 53, I, iodin, iodine.

iodine-131 (noun)	radioisotope (noun)
heavy radioactive isotope of iodine with a half-life of 8 days; used in a sodium salt to diagnose thyroid disease and to treat goiter	a radioactive isotope of an element; produced either naturally or artificially