A narrowing in any of the natural passages of the body, such as the OESOPHAGUS, the INTESTINE or the URETHRA. It may be due to the development of a growth in the wall of the passage affected, or to pressure upon it by such a growth in some neighbouring organ, but in the majority of cases a stricture is the result of previous ulceration on the inner surface of the passage, followed by contraction of the resultant scar. (See INTESTINE, DISEASES OF; URETHRA, DISEASES OF AND INJURY TO.)