Department of Energy vs Energy

Department of Energy and Energy both are nouns.

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

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

Department of Energy and Energy: the federal department responsible for maintaining a national energy policy of the United States; created in 1977

Other synonyms of Department of Energy include DOE, Energy Department.

Department of Energy (noun)	Energy (noun)
the federal department responsible for maintaining a national energy policy of the United States; created in 1977	the federal department responsible for maintaining a national energy policy of the United States; created in 1977