Air Force vs Defense Department

Air Force and Defense Department both are nouns.

Word	Noun	Adjective	Verb	Adverb
Air Force	Yes	No	No	No
Defense Department	Yes	No	No	No

Air Force (noun)	Defense Department (noun)
the airforce of the United States of America; the agency that defends the United States through control and exploitation of air and space	the federal department responsible for safeguarding national security of the United States; created in 1947