Penis: The external reproductive organ of males. It is composed of a mass of erectile tissue enclosed in three cylindrical fibrous compartments. Two of the three compartments, the corpus cavernosa, are placed side-by-side along the upper part of the organ. The third compartment below, the corpus spongiosum, houses the urethra.Penile Neoplasms: Cancers or tumors of the PENIS or of its component tissues.Penile Erection: The state of the PENIS when the erectile tissue becomes filled or swollen (tumid) with BLOOD and causes the penis to become rigid and elevated. It is a complex process involving CENTRAL NERVOUS SYSTEM; PERIPHERAL NERVOUS SYSTEMS; HORMONES; SMOOTH MUSCLES; and vascular functions.Erectile Dysfunction: The inability in the male to have a PENILE ERECTION due to psychological or organ dysfunction.Clitoris: An erectile structure homologous with the penis, situated beneath the anterior labial commissure, partially hidden between the anterior ends of the labia minora.Penile Induration: A condition characterized by hardening of the PENIS due to the formation of fibrous plaques on the dorsolateral aspect of the PENIS, usually involving the membrane (tunica albuginea) surrounding the erectile tissue (corpus cavernosum penis). This may eventually cause a painful deformity of the shaft or constriction of the urethra, or both.Balanitis: Inflammation of the head of the PENIS, glans penis.Priapism: A prolonged painful erection that may lasts hours and is not associated with sexual activity. It is seen in patients with SICKLE CELL ANEMIA, advanced malignancy, spinal trauma; and certain drug treatments.Scrotum: A cutaneous pouch of skin containing the testicles and spermatic cords.Penile Prosthesis: Rigid, semi-rigid, or inflatable cylindric hydraulic devices, with either combined or separate reservoir and pumping systems, implanted for the surgical treatment of organic ERECTILE DYSFUNCTION.Urologic Surgical Procedures, Male: Surgery performed on the male genitalia.Genitalia, Male: The male reproductive organs. They are divided into the external organs (PENIS; SCROTUM;and URETHRA) and the internal organs (TESTIS; EPIDIDYMIS; VAS DEFERENS; SEMINAL VESICLES; EJACULATORY DUCTS; PROSTATE; and BULBOURETHRAL GLANDS).Circumcision, Male: Excision of the prepuce of the penis (FORESKIN) or part of it.Tuberculosis, Male Genital: MYCOBACTERIUM infections of the male reproductive tract (GENITALIA, MALE).Hypospadias: A birth defect due to malformation of the URETHRA in which the urethral opening is below its normal location. In the male, the malformed urethra generally opens on the ventral surface of the PENIS or on the PERINEUM. In the female, the malformed urethral opening is in the VAGINA.Copulation: Sexual union of a male and a female in non-human species.Penile Implantation: Surgical insertion of cylindric hydraulic devices for the treatment of organic ERECTILE DYSFUNCTION.Genital Diseases, Male: Pathological processes involving the male reproductive tract (GENITALIA, MALE).Genitalia: The external and internal organs related to reproduction.