A period, also called menstruation, is the regular release of blood and tissue from the inner lining of the uterus through the vagina. It typically occurs about once a month as part of the menstrual cycle, which prepares the body for a possible pregnancy
. During the menstrual cycle, hormones cause the lining of the uterus to thicken in preparation for a fertilized egg to implant. If fertilization does not occur, the lining breaks down and is shed from the body as menstrual blood, resulting in a period
. Periods usually start around age 12 but can begin anytime between 8 and 16 years old. They typically last between 2 and 7 days, with most women bleeding for about 3 to 5 days. The menstrual cycle length varies but averages about 28 days, ranging normally from 21 to 35 days
. In summary, a period is a natural, monthly process where the uterus sheds its lining through vaginal bleeding, signaling that pregnancy has not occurred and marking a key part of female reproductive health
