Residual root

Residual \Re*sid"u*al\ (r?-z?d"?-al), a. [See {Residue}.]
   Pertaining to a residue; remaining after a part is taken.
   [1913 Webster]

   {Residual air} (Physiol.), that portion of air contained in
      the lungs which can not be expelled even by the most
      violent expiratory effort. It amounts to from 75 to 100
      cubic inches. Cf. {Supplemental air}, under
      {Supplemental}.

   {Residual error}. (Mensuration) See {Error}, 6
   (b) .

   {Residual figure} (Geom.), the figure which remains after a
      less figure has been taken from a greater one.

   {Residual magnetism} (Physics), remanent magnetism. See under
      {Remanent}.

   {Residual product}, a by product, as cotton waste from a
      cotton mill, coke and coal tar from gas works, etc.

   {Residual quantity} (Alg.), a binomial quantity the two parts
      of which are connected by the negative sign, as a-b.

   {Residual root} (Alg.), the root of a residual quantity, as
      [root](a-b).
      [1913 Webster]