religious vs pious

religious is a noun but pious is not a noun.

Word	Noun	Adjective	Verb	Adverb
religious	Yes	Yes	No	No
pious	No	Yes	No	No

religious (noun)	pious (noun)
a member of a religious order who is bound by vows of poverty and chastity and obedience

religious (adjective)	pious (adjective)
having or showing belief in and reverence for a deity	having or showing or expressing reverence for a deity
of or relating to clergy bound by monastic vows
concerned with sacred matters or religion or the church
extremely scrupulous and conscientious