HHS vs executive department

HHS and executive department both are nouns.

Word	Noun	Adjective	Verb	Adverb
HHS	Yes	No	No	No
executive department	Yes	No	No	No

As nouns, executive department is a hypernym of HHS; that is, executive department is a word with a broader meaning than HHS:

HHS: the United States federal department that administers all federal programs dealing with health and welfare; created in 1979
executive department: a federal department in the executive branch of the government of the United States

HHS (noun)	executive department (noun)
the United States federal department that administers all federal programs dealing with health and welfare; created in 1979	a federal department in the executive branch of the government of the United States