Gynecology: The medical practice specializing in women's health and in diseases of the female reproductive and sexual organs.

Hormones: Chemicals that guide the changes in our bodies and influence how glands and organs work.

Menarche: The initial onset of menstrual periods in a young woman.

Menstruation: The sloughing off of the built-up uterine lining that takes place if conception has not occurred.

Ovaries: Female gonads that produce ova and sex hormones.

Ovulation: The release of a mature ovum from the ovary.

Pap Smear: A screening test for cancer of cells from the cervix.

Premenstrual syndrome (PMS): Symptoms of physical discomfort and emotional irritability that occur days before menstruation begins.

Puberty: A period of rapid physical changes (such as breast enlargement in girls and facial hair growth in boys) in early adolescense during which the reproductive organs mature.

Vagina: A stretchable canal in the female that opens at the vulva and extends about four inches into the pelvis.