The End of Female Fertility
For a female, menopause is a natural part of the lifecycle. As a young woman, she would have begun to have a monthly period, which marked the beginning of her ability to conceive a child. Menopause is, technically the cessation of a woman's menstrual cycle.
Once a woman has entered menopause, she will no longer ovulate, can no longer become pregnant, and no longer has a monthly period. Most women enter menopause sometime between age 45 and 55, though there are some factors that can cause a woman to enter menopause considerably earlier.
Women in the western world tend to enter menopause much later than those that live in less developed parts of the world.