donor vs blood donor

donor and blood donor both are nouns.

Word	Noun	Adjective	Verb	Adverb
donor	Yes	No	No	No
blood donor	Yes	No	No	No

As nouns, blood donor is a hyponym of donor; that is, blood donor is a word with a more specific, narrower meaning than donor:

donor: (medicine) someone who gives blood or tissue or an organ to be used in another person (the host)
blood donor: someone who gives blood to be used for transfusions

Other hyponyms of donor include organ donor.

donor (noun)	blood donor (noun)
person who makes a gift of property	someone who gives blood to be used for transfusions
(medicine) someone who gives blood or tissue or an organ to be used in another person (the host)