junior-grade vs junior

junior-grade is not a noun while junior is a noun.

Word	Noun	Adjective	Verb	Adverb
junior-grade	No	Yes	No	No
junior	Yes	Yes	No	No

junior-grade (noun)	junior (noun)
	the younger of two persons
	a third-year undergraduate
	term of address for a disrespectful and annoying male

junior-grade (adjective)	junior (adjective)
inferior in rank or status	younger; lower in rank; shorter in length of tenure or service
	used of the third or next to final year in United States high school or college
	including or intended for youthful persons