menstruation vs catamenia

menstruation and catamenia both are nouns.

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

As nouns, menstruation and catamenia are synonyms defined as:

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

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

menstruation (noun)	catamenia (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