What is "residual quantity"

Residual \Re*sid"u*al\ (r?-z?d"?-al),

1. [See Residue.] Pertaining to a residue; remaining after a part is taken.

   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-

2. Residual root (Alg.), the root of a residual quantity, as [root](a-b).