The menstrual cycle is a process by which your body gets ready for pregnancy (123).
It begins during puberty at around age 9-12 and continues through to menopause (which is the end of menstruation) around the age of 45-50. (123).
The menstrual cycle repeats every month - about every 28-31 days. Since everybody is different, it is completely normal for some people to have longer or shorter menstrual cycles.
An average menstrual cycle usually ranges between 21-35 days (17).