Moth·er, n.  A film or membrane which is developed on the surface of fermented alcoholic liquids, such as vinegar, wine, etc., and acts as a means of conveying the oxygen of the air to the alcohol and other combustible principles of the liquid, thus leading to their oxidation.
 Note: ☞ The film is composed of a mass of rapidly developing microorganisms of the genus Mycoderma, and in the mother of vinegar the microorganisms (Mycoderma aceti) composing the film are the active agents in the Conversion of the alcohol into vinegar. When thickened by growth, the film may settle to the bottom of the fluid. See Acetous fermentation, under Fermentation.
 Vin·e·gar n.
 1. A sour liquid used as a condiment, or as a preservative, and obtained by the spontaneous (acetous) fermentation, or by the artificial oxidation, of wine, cider, beer, or the like.
 Note: ☞ The characteristic sourness of vinegar is due to acetic acid, of which it contains from three to five per cent. Wine vinegar contains also tartaric acid, citric acid, etc.
 2. Hence, anything sour; -- used also metaphorically.
    Here's the challenge: . . . I warrant there's vinegar and pepper in't.   --Shak.
 Aromatic vinegar, strong acetic acid highly flavored with aromatic substances.
 Mother of vinegar. See 4th Mother.
 Radical vinegar, acetic acid.
 Thieves' vinegar. See under Thief.
 Vinegar eel Zool., a minute nematode worm (Leptodera oxophila, or Anguillula acetiglutinis), commonly found in great numbers in vinegar, sour paste, and other fermenting vegetable substances; -- called also vinegar worm.
 Vinegar lamp Chem., a fanciful name of an apparatus designed to oxidize alcohol to acetic acid by means of platinum.
 Vinegar plant. See 4th Mother.
 Vinegar tree Bot., the stag-horn sumac (Rhus typhina), whose acid berries have been used to intensify the sourness of vinegar.
 Wood vinegar. See under Wood.