USAF vs Department of Defense

USAF and Department of Defense both are nouns.

Word	Noun	Adjective	Verb	Adverb
USAF	Yes	No	No	No
Department of Defense	Yes	No	No	No

USAF (noun)	Department of Defense (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