menstrual hygiene

Menstrual

The menstrual cycle starts with menstruation. The firswt day of your menstrual cycle is considered to be the first day of true bleeding during your menstrual phase.

The menstrual cycle is the reproductive cycle, as long as she is fertile she is always on her menstrual cycle. You can't tell where she is in her menstrual cycle unless she tells you.

You've sort of answered this question twice in the question itself!

"The PERIOD in the MENSTRUAL cycle which the...in the MENSTRUAL"

The menstrual phase aka menstruation or period.