Dark Ages vs age

Dark Ages and age both are nouns.

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

Dark Ages (noun)	age (noun)
the period of history between classical antiquity and the Italian Renaissance	how long something has existed
	a time of life (usually defined in years) at which some particular qualification or power arises
	a late time of life
	an era of history having some distinctive feature
	a prolonged period of time