Final answer:
Amenorrhea is the term used to describe the failure to have a menstrual period, and it can occur due to a variety of conditions affecting women of reproductive age.
Step-by-step explanation:
Failure to have a menstrual period is called amenorrhea. Menstruation, also known as the menstrual period or menses, is the process in which the endometrium of the uterus is shed through the vagina during the first several days of the menstrual cycle if fertilization has not occurred. Amenorrhea is where there is an absence of menstrual periods in a woman of reproductive age. This could be due to various conditions including hormonal imbalances, eating disorders, excessive exercise, or chronic diseases. It's crucial to differentiate this from the menstrual cycle's natural conclusion, which typically occurs when a woman is around 50 years old, a phase known as menopause. Additionally, the onset of the first menstrual period is referred to as menarche, occurring in pubertal females.