Source : Webster's Revised Unabridged Dictionary (1913)

   4. To bring to a certain state or condition by grinding,
      pounding, kneading, rubbing, etc.; as, to reduce a
      substance to powder, or to a pasty mass; to reduce fruit,
      wood, or paper rags, to pulp.

            It were but right And equal to reduce me to my dust.
                                                  --Milton.

   5. To bring into a certain order, arrangement,
      classification, etc.; to bring under rules or within
      certain limits of descriptions and terms adapted to use in
      computation; as, to reduce animals or vegetables to a
      class or classes; to reduce a series of observations in
      astronomy; to reduce language to rules.

   6. (Arith.)
      (a) To change, as numbers, from one denomination into
          another without altering their value, or from one
          denomination into others of the same value; as, to
          reduce pounds, shillings, and pence to pence, or to
          reduce pence to pounds; to reduce days and hours to
          minutes, or minutes to days and hours.
      (b) To change the form of a quantity or expression without
          altering its value; as, to reduce fractions to their
          lowest terms, to a common denominator, etc.

   7. (Chem.) To bring to the metallic state by separating from
      impurities; hence, in general, to remove oxygen from; to
      deoxidize; to combine with, or to subject to the action
      of, hydrogen; as, ferric iron is reduced to ferrous iron;
      or metals are reduced from their ores; -- opposed to
      {oxidize}.

   8. (Med.) To restore to its proper place or condition, as a
      displaced organ or part; as, to reduce a dislocation, a
      fracture, or a hernia.

   {Reduced iron} (Chem.), metallic iron obtained through
      deoxidation of an oxide of iron by exposure to a current
      of hydrogen or other reducing agent. When hydrogen is used
      the product is called also {iron by hydrogen}.

   {To reduce an equation} (Alg.), to bring the unknown quantity
      by itself on one side, and all the known quantities on the
      other side, without destroying the equation.

   {To reduce an expression} (Alg.), to obtain an equivalent
      expression of simpler form.

   {To reduce a square} (Mil.), to reform the line or column
      from the square.

   Syn: To diminish; lessen; decrease; abate; shorten; curtail;
        impair; lower; subject; subdue; subjugate; conquer.