Department of Defense vs Defense

Department of Defense and Defense both are nouns.

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

As nouns, Department of Defense and Defense are synonyms defined as:

Department of Defense and Defense: the federal department responsible for safeguarding national security of the United States; created in 1947

Other synonyms of Department of Defense include Defense Department, DoD, United States Department of Defense.

Department of Defense (noun)	Defense (noun)
the federal department responsible for safeguarding national security of the United States; created in 1947	the federal department responsible for safeguarding national security of the United States; created in 1947