menstruation vs menstruum

menstruation and menstruum both are nouns.

Word	Noun	Adjective	Verb	Adverb
menstruation	Yes	No	No	No
menstruum	Yes	No	No	No

As nouns, menstruation and menstruum are synonyms defined as:

menstruation and menstruum: the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause

Other synonyms of menstruation include catamenia, flow, menses, period.

menstruation (noun)	menstruum (noun)
the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause	the monthly discharge of blood from the uterus of nonpregnant women from puberty to menopause
	(archaic) a solvent