registered nurse vs RN

registered nurse and RN both are nouns.

Word	Noun	Adjective	Verb	Adverb
registered nurse	Yes	No	No	No
RN	Yes	No	No	No

As nouns, registered nurse and RN are synonyms defined as:

registered nurse and RN: a graduate nurse who has passed examinations for registration

registered nurse (noun)	RN (noun)
a graduate nurse who has passed examinations for registration	a graduate nurse who has passed examinations for registration