Amenorrhea is the lack of menstruation in a woman of reproductive age. It can be caused by many other things like problems with reproductive organs, hormonal disturbances, poor nutrition, stress or extreme fatness/thinness. Depending on the cause, amenorrhea may be curable-if you are experiencing it see a doctor. A woman is probably infertile while she has amenorrhea. It is normal for pregnant/breastfeeding women to not menstruate.
Attribution: Straight Talk Foundation