junior vs lowly

junior is a noun but lowly is not a noun.

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

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

junior (adjective)	lowly (adjective)
younger; lower in rank; shorter in length of tenure or service	low or inferior in station or quality
used of the third or next to final year in United States high school or college	inferior in rank or status
including or intended for youthful persons	of low birth or station (`base' is archaic in this sense)
	used of unskilled work (especially domestic work)