nuclear physicist vs physicist

nuclear physicist and physicist both are nouns.

Word	Noun	Adjective	Verb	Adverb
nuclear physicist	Yes	No	No	No
physicist	Yes	No	No	No

As nouns, physicist is a hypernym of nuclear physicist; that is, physicist is a word with a broader meaning than nuclear physicist:

nuclear physicist (noun)	physicist (noun)
a physicist who specializes in nuclear physics	a scientist trained in physics