age vs reign

age and reign both are nouns.

Word	Noun	Adjective	Verb	Adverb
age	Yes	No	Yes	No
reign	Yes	No	Yes	No

As nouns, reign is a hyponym of age; that is, reign is a word with a more specific, narrower meaning than age:

Other hyponyms of age include antiquity, golden age, Jazz Age, turn of the century, literary period.

age (noun)	reign (noun)
how long something has existed	royal authority; the dominion of a monarch
a time of life (usually defined in years) at which some particular qualification or power arises	the period during which a monarch is sovereign
a late time of life	a period during which something or somebody is dominant or powerful
an era of history having some distinctive feature
a prolonged period of time

age (verb)	reign (verb)
grow old or older	have sovereign power
begin to seem older; get older	be larger in number, quantity, power, status or importance
make older