an acid with one unit of water removed
a water reactive compound that gives an acid or a base when combined with water
These are compounds formed by the removal of water or Hydrogen and Oxygen together from another substance. In inorganic chemistry most anhydrides are formed by the loss of the water of crystallisation. eg. Copper(II) sulphate is a blue hydrated salt with the formula CuSO4.5H2O, but if heated, the water is driven off leaving the colourless anhydrous salt CuSO4. In organic chemistry an anhydride is usually the result of the loss of a water molecule from a dicarboxylic acid, eg. from phthalic acid to give phthalic anhydride (see below)
Any chemical compound obtained, either in practice or in principle, by the elimination of water from another compound.
In chemistry, an anhydride is a compound that can be considered as derived from another compound by subtracting the molecules of water.