Penectomy: The surgical removal of the penis. In a partial penectomy, part of the penis is removed. In a total penectomy, the whole penis is removed.
Penetration: The insertion of an erect penis into a woman's vagina.
Penis: One of the external structures of the male reproductive system, along with the scrotum and testicles.
Perineum: The space between the opening of the rectum and the scrotum in the male and the opening of the rectum and the vulva in the female.
Peritoneum: The lining of the abdominal cavity.
Peyronie's disease: A condition in which a plaque, or hard lump, forms on the penis. The hardened plaque reduces flexibility, causing pain and forcing the penis to bend or arc during erection.
Phimosis: A condition in which the foreskin of the penis becomes constricted and difficult to retract.
The Pill: A drug containing hormones which women take to prevent pregnancy. Also known as birth control pills.
Polycystic ovary syndrome (PCOS): A common disorder in women caused by a hormonal imbalance. Symptoms of PCOS include irregular or no periods, acne, obesity, and excess hair growth. This disorder often prevents ovulation (the release of an oocyte by the ovary), leading to infertility.
Premature ejaculation: Ejaculation that occurs before or soon after penetration.
Premenstrual syndrome (PMS): A combination of physical and mood disturbances that occur after ovulation and normally end with the onset of the menstrual flow.
Premenstrual dysphoric disorder (PMDD): A severe form of PMS. The symptoms of PMDD are similar to those of PMS, but are severe enough to interfere with work, social activities, and relationships.
Prepuce: The fold of skin that covers the head of the penis (also called the foreskin). Prepuce is also the hood or covering of the clitoris.
Priapism: A persistent, often painful erection that can last from several hours to a few days.
Primary amenorrhea: A condition in which a young woman never gets her first period.
Proctoscopy: An exam of the rectum.
Prognosis: Chance of recovery from an injury or disease.
Progesterone: A female hormone that acts to prepare the uterus (the womb) to receive and sustain a fertilized egg.