menstrual blood vs menorrhea

menstrual blood and menorrhea both are nouns.

Word	Noun	Adjective	Verb	Adverb
menstrual blood	Yes	No	No	No
menorrhea	Yes	No	No	No

As nouns, menstrual blood and menorrhea are synonyms defined as:

menstrual blood and menorrhea: flow of blood from the uterus; occurs at roughly monthly intervals during a woman's reproductive years

Other synonyms of menstrual blood include menstrual flow.

menstrual blood (noun)	menorrhea (noun)
flow of blood from the uterus; occurs at roughly monthly intervals during a woman's reproductive years	flow of blood from the uterus; occurs at roughly monthly intervals during a woman's reproductive years