RN vs registered nurse

RN and registered nurse both are nouns.

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

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

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

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