What is menstruation? What is menses?

Menstruation and menses mean the same thing.

What is menstruation or menses?

Menstruation or menses is a normal physiological process in a woman's reproductive cycle, in which the inner lining of the uterus (endometrium) breaks down each month and exits through the vagina along with blood.

Simply put, menstruation and menses can be explained in 3–4 sentences:

1. Each month, a healthy woman's body builds a new lining inside the uterus in preparation for pregnancy.
2. If pregnancy doesn't occur, this extra lining is no longer needed.
3. So it leaves the body along with blood — this is menstruation or menses.
4. Menstruation usually begins between the ages of 8–18 and continues until about 45–50 years of age.

In other words, menstruation = menses = the shedding of the uterine lining during a woman's monthly reproductive cycle.