polycythemia vs blood disorder

polycythemia and blood disorder both are nouns.

Word	Noun	Adjective	Verb	Adverb
polycythemia	Yes	No	No	No
blood disorder	Yes	No	No	No

As nouns, blood disorder is a hypernym of polycythemia; that is, blood disorder is a word with a broader meaning than polycythemia:

polycythemia: a disorder characterized by an abnormal increase in the number of red blood cells in the blood
blood disorder: a disease or disorder of the blood

Other hypernyms of polycythemia include blood disease.

polycythemia (noun)	blood disorder (noun)
a disorder characterized by an abnormal increase in the number of red blood cells in the blood	a disease or disorder of the blood