young vs junior

young and junior both are nouns.

Word	Noun	Adjective	Verb	Adverb
young	Yes	Yes	No	No
junior	Yes	Yes	No	No

young (noun)	junior (noun)
any immature animal	the younger of two persons
young people collectively	a third-year undergraduate
	term of address for a disrespectful and annoying male

young (adjective)	junior (adjective)
(used of living things especially persons) in an early period of life or development or growth	younger; lower in rank; shorter in length of tenure or service
(of crops) harvested at an early stage of development; before complete maturity	used of the third or next to final year in United States high school or college
not tried or tested by experience	including or intended for youthful persons
being in its early stage
suggestive of youth; vigorous and fresh