run-of-the-mill vs ordinary

run-of-the-mill is not a noun while ordinary is a noun.

Word	Noun	Adjective	Verb	Adverb
run-of-the-mill	No	Yes	No	No
ordinary	Yes	Yes	No	No

run-of-the-mill (noun)	ordinary (noun)
	(heraldry) any of several conventional figures used on shields
	an early bicycle with a very large front wheel and small back wheel
	a clergyman appointed to prepare condemned prisoners for death
	a judge of a probate court
	the expected or commonplace condition or situation

run-of-the-mill (adjective)	ordinary (adjective)
not special in any way; lacking distinction	not exceptional in any way especially in quality or ability or size or degree
	lacking special distinction, rank, or status; commonly encountered