RBC vs red blood cell

RBC and red blood cell both are nouns.

Word	Noun	Adjective	Verb	Adverb
RBC	Yes	No	No	No
red blood cell	Yes	No	No	No

As nouns, RBC and red blood cell are synonyms defined as:

RBC and red blood cell: a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus

Other synonyms of RBC include erythrocyte.

RBC (noun)	red blood cell (noun)
a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus	a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus