red blood cell vs RBC

red blood cell and RBC both are nouns.

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

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

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

Other synonyms of red blood cell include erythrocyte.

red blood cell (noun)	RBC (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