Vinegar (from Old French vinaigre "sour wine") is a sour liquid made from the oxidation of ethanol in wine, cider, beer, or the like. Vinegar is typically 3-5% by volume acetic acid, though natural vinegars also contain tartaric acid, citric acid, and others.
It is commonly used in food preparations, particularly in vinaigrettes, and in the pickling process. It is also used as a comdiment (for example, the British commonly use vinegar on fried potatoes; Americans often use it on fish).
Some forms of simple "white" vinegar may be nothing more than solutions of acetic acid in water.