phlebotomy vs bloodletting

phlebotomy and bloodletting both are nouns.

Word	Noun	Adjective	Verb	Adverb
phlebotomy	Yes	No	No	No
bloodletting	Yes	No	No	No

As nouns, bloodletting is a hypernym of phlebotomy; that is, bloodletting is a word with a broader meaning than phlebotomy:

phlebotomy: surgical incision into a vein; used to treat hemochromatosis
bloodletting: formerly used as a treatment to reduce excess blood (one of the four humors of medieval medicine)

Other hypernyms of phlebotomy include incision, section, surgical incision.

phlebotomy (noun)	bloodletting (noun)
surgical incision into a vein; used to treat hemochromatosis	formerly used as a treatment to reduce excess blood (one of the four humors of medieval medicine)
	indiscriminate slaughter