junior-grade vs petty

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

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

As adjectives, junior-grade and petty are synonyms defined as:

Other synonyms of junior-grade include lower-ranking, lowly, secondary, subaltern.

junior-grade (noun)	petty (noun)
	larceny of property having a value less than some amount (the amount varies by locale)

junior-grade (adjective)	petty (adjective)
inferior in rank or status	inferior in rank or status
	contemptibly narrow in outlook
	(informal) small and of little importance