The term 'menstruation' and 'menses' are derived from the Latin mensis meaning month. The time between each menses is colloquially called a menstrual period and the proper medical term is menses . Menstruation is a monthly shedding of a female's uterine lining which is the inner layer of the womb;the cells that line the womb{uterus}. The menstruation should last about 3 to 5 days. It contains blood and tissue that exits the woman's body through the vagina. Day 1 is the first day of your menses while day 14 is the day you ovulate depending on your cycle. When the egg is not fertilized, hormone levels drop and at about day 25, the egg dissolves and cycle begins again at day 30. The cycle usually varies in length from about 2 to 7 days but with time, it regulates. We have abnormalities during periods like amenorrhea [no period], dysmenorrhea [painful period] and abnormal bleeding. The average age for a girl's first period is 12 but the usual range of age i