An instance of menstruation, the part of each month during which a fertile woman menstruates.
The periodic discharging of the menses, the flow of blood and cells from the lining of the uterus in unfertilized females of humans and other primates.
red sails in the sunset
How often have the words menstruation and red sails in the sunset occurred in a corpus of books? (source: Google Ngram Viewer )