iodine-125 vs radioisotope

iodine-125 and radioisotope both are nouns.

Word	Noun	Adjective	Verb	Adverb
iodine-125	Yes	No	No	No
radioisotope	Yes	No	No	No

As nouns, radioisotope is a hypernym of iodine-125; that is, radioisotope is a word with a broader meaning than iodine-125:

iodine-125: light radioactive isotope of iodine with a half-life of 60 days; used as a tracer in thyroid studies and as a treatment for hyperthyroidism
radioisotope: a radioactive isotope of an element; produced either naturally or artificially

Other hypernyms of iodine-125 include atomic number 53, I, iodin, iodine.

iodine-125 (noun)	radioisotope (noun)
light radioactive isotope of iodine with a half-life of 60 days; used as a tracer in thyroid studies and as a treatment for hyperthyroidism	a radioactive isotope of an element; produced either naturally or artificially