menses vs menstruum

menses and menstruum both are nouns.

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

As nouns, menses and menstruum are synonyms defined as:

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

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

menses (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