catamenia vs menstruation

catamenia and menstruation both are nouns.

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

As nouns, catamenia and menstruation are synonyms defined as:

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

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

catamenia (noun)	menstruation (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