Middle Ages vs Dark Ages

Middle Ages and Dark Ages both are nouns.

Word	Noun	Adjective	Verb	Adverb
Middle Ages	Yes	No	No	No
Dark Ages	Yes	No	No	No

As nouns, Middle Ages and Dark Ages are synonyms defined as:

Middle Ages and Dark Ages: the period of history between classical antiquity and the Italian Renaissance

Middle Ages (noun)	Dark Ages (noun)
the period of history between classical antiquity and the Italian Renaissance	the period of history between classical antiquity and the Italian Renaissance