What's the difference between i.e. and e.g.?
c.1400, from Old French ulcere, from Vulgar Latin ulcerem, from Latin ulcus (genitive ulceris) "ulcer," from PIE *elk-es- "wound" (cf. Greek elkos).
ulcer ul·cer (ŭl'sər)
A lesion of the skin or of a mucous membrane, such as the one lining the stomach or duodenum, that is accompanied by formation of pus and necrosis of surrounding tissue, usually resulting from inflammation or ischemia.
Note: It used to be thought that stress was the cause of stomach and duodenal ulcers, but we now know that they are caused by bacteria and can be cured by antibiotics.