Amenorrhea: The absence of menstrual periods in women of reproductive age.

Egg: The female reproductive cell made in and released from the ovaries. Also called the ovum.

Fallopian Tubes: Tubes through which an egg travels from the ovary to the uterus.

Hormones: Substances made in the body that control the function of cells or organs.

Ovaries: Organs in women that contain the eggs necessary to get pregnant and make important hormones, such as estrogen, progesterone, and testosterone.

Ovulation: The time when an ovary releases an egg.

Puberty: The stage of life when the reproductive organs start to function and other sex features develop. For women, this is the time when menstrual periods start and the breasts develop.

Sperm: A cell made in the male testicles that can fertilize a female egg.

Toxic Shock Syndrome: A severe illness caused by a bacterial infection. It can be caused by leaving a tampon in the vagina too long.

Uterus: A muscular organ in the female pelvis. During pregnancy, this organ holds and nourishes the fetus.

Vagina: A tube-like structure surrounded by muscles. The vagina leads from the uterus to the outside of the body.