RBC vs corpuscle

RBC and corpuscle both are nouns.

Word	Noun	Adjective	Verb	Adverb
RBC	Yes	No	No	No
corpuscle	Yes	No	No	No

As nouns, corpuscle is a hypernym of RBC; that is, corpuscle is a word with a broader meaning than RBC:

RBC: a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus
corpuscle: either of two types of cells (erythrocytes and leukocytes) and sometimes including platelets

Other hypernyms of RBC include blood cell, blood corpuscle.

RBC (noun)	corpuscle (noun)
a mature blood cell that contains hemoglobin to carry oxygen to the bodily tissues; a biconcave disc that has no nucleus	either of two types of cells (erythrocytes and leukocytes) and sometimes including platelets
	(nontechnical usage) a tiny piece of anything