age vs immature

age is a noun but immature is not a noun.

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

age (noun)	immature (noun)
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

age (adjective)	immature (adjective)
	not yet mature
	characteristic of a lack of maturity
	(used of living things especially persons) in an early period of life or development or growth
	(of birds) not yet having developed feathers
	not fully developed or mature; not ripe