lower-ranking vs secondary

lower-ranking is not a noun while secondary is a noun.

Word	Noun	Adjective	Verb	Adverb
lower-ranking	No	Yes	No	No
secondary	Yes	Yes	No	No

As adjectives, lower-ranking and secondary are synonyms defined as:

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

lower-ranking (noun)	secondary (noun)
	coil such that current is induced in it by passing a current through the primary coil
	the defensive football players who line up behind the linemen

lower-ranking (adjective)	secondary (adjective)
inferior in rank or status	being of second rank or importance or value; not direct or immediate
	depending on or incidental to what is original or primary
	inferior in rank or status
	not of major importance
	belonging to a lower class or rank