An ulcer is a hole in the wall of an organ, and ulcers originating in the stomach or in the organs immediately bordering it are termed peptic ulcers. The ones within the stomach are called gastric ulcers; those a bit higher up than the stomach are esophageal, and those at the border of the stomach and the intestine are duodenal (the most common of peptic ulcers). Photomicrograph of a stomach ulcer.
