An area of tissue erosion, for example, of the skin or lining of the gastrointestinal (GI) tract.
Due to the erosion, an ulcer is concave. It is always depressed below the level of the surrounding tissue.
Ulcers can have diverse causes. Ulcers on the skin are often due to irritation, as with bedsores, and they may become infected and inflamed as they grow.
Ulcers in the GI tract were once attributed to stress but most are now believed to be due to infection with the bacteria H. pyloridus. GI ulcers, however, may be made worse by stress, smoking and other noninfectious factors.
The word "ulcer" traveled across the English Channel from the French "ulcere" which, in turn, came from the Latin "ulcus, ulceris" meaning "sore, sore spot, painful spot, or ulcer."
