junior-grade vs lowly

junior-grade and lowly both are adjectives.

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

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

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

junior-grade (adjective)	lowly (adjective)
inferior in rank or status	low or inferior in station or quality
	inferior in rank or status
	of low birth or station (`base' is archaic in this sense)
	used of unskilled work (especially domestic work)