NCDC vs federal agency

NCDC and federal agency both are nouns.

Word	Noun	Adjective	Verb	Adverb
NCDC	Yes	No	No	No
federal agency	Yes	No	No	No

As nouns, federal agency is a hypernym of NCDC; that is, federal agency is a word with a broader meaning than NCDC:

NCDC: the part of NOAA that maintains the world's largest active archive of weather data
federal agency: an administrative unit of government

Other hypernyms of NCDC include agency, authority, bureau, government agency, office.

NCDC (noun)	federal agency (noun)
the part of NOAA that maintains the world's largest active archive of weather data	an administrative unit of government