nuclear physicist vs Niels Bohr

nuclear physicist and Niels Bohr both are nouns.

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

nuclear physicist (noun)	Niels Bohr (noun)
a physicist who specializes in nuclear physics	Danish physicist who studied atomic structure and radiations; the Bohr theory of the atom accounted for the spectrum of hydrogen (1885-1962)