residue

noun

1. (countable, uncountable)That which persists or remains following the removal or elimination of other elements.
2. (countable, uncountable)The substance that remains after evaporation, distillation, filtration or any similar process.
3. (countable, uncountable)A molecule that is released from a polymer after bonds between neighbouring monomers are broken, such as an amino acid in a polypeptide chain.
4. (countable, uncountable)Whatever property or effects are left in an estate after payment of all debts, other charges and deduction of what is specifically bequeathed by the testator.
5. (countable, uncountable)A representative element of an equivalence class modulo some base, conventionally in the half-open interval from zero to the base; the nonnegative remainder after dividing a number by a base.
6. (countable, uncountable)A form of complex number, proportional to the contour integral of a meromorphic function along a path enclosing one of its singularities.

   “By taking residues, we can represent this integral in terms of a Jackson integral.”