Menopause is defined as the state of an absence of menstrual periods for 12 months. The menopausal transition starts with varying menstrual cycle length and ends with the final menstrual period. Perimenopause is a term sometimes used and means "the time around menopause." It is often used to refer to the menopausal transitional period. It is not officially a medical term, but is sometimes used to explain certain aspects of the menopause transition in lay terms. "Postmenopausal" is a term used to as an adjective to refer to the time after menopause has occurred. For example, doctors may speak of a condition that occurs in "postmenopausal women." This refers to women who have already reached menopause.

Menopause is the time in a woman's life when the function of the ovaries ceases and she can no longer become pregnant. The ovary (female gonad), is one of a pair of reproductive glands in women. They are located in the pelvis, one on each side of the uterus. Each ovary is about the size and shape of an almond. The ovaries produce eggs (ova) and female hormones such as estrogen. During each monthly menstrual cycle, an egg is released from one ovary. The egg travels from the ovary through a Fallopian tube to the uterus.