religious vs nun

religious and nun both are nouns.

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

As nouns, nun is a hyponym of religious; that is, nun is a word with a more specific, narrower meaning than religious:

religious: a member of a religious order who is bound by vows of poverty and chastity and obedience
nun: a woman religious

Other hyponyms of religious include friar, mendicant, monastic, monk, Benedictine, Jesuit, eremite, cenobite, coenobite, superior, votary.

religious (noun)	nun (noun)
a member of a religious order who is bound by vows of poverty and chastity and obedience	a buoy resembling a cone
	a woman religious
	the 14th letter of the Hebrew alphabet

religious (adjective)	nun (adjective)
having or showing belief in and 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