The Collaborative International Dictionary of English v.0.48:

Residual \Re*sid"u*al\ (r?-z?d"?-al), a. [See Residue.]
   Pertaining to a residue; remaining after a part is taken.
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   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).
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The Collaborative International Dictionary of English v.0.48:

Error \Er"ror\, n. [OF. error, errur, F. erreur, L. error, fr.
   errare to err. See Err.]
   1. A wandering; a roving or irregular course. [Obs.]
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            The rest of his journey, his error by sea. --B.
                                                  Jonson.
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   2. A wandering or deviation from the right course or
      standard; irregularity; mistake; inaccuracy; something
      made wrong or left wrong; as, an error in writing or in
      printing; a clerical error.
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   3. A departing or deviation from the truth; falsity; false
      notion; wrong opinion; mistake; misapprehension.
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            His judgment was often in error, though his candor
            remained unimpaired.                  --Bancroft.
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   4. A moral offense; violation of duty; a sin or
      transgression; iniquity; fault. --Ps. xix. 12.
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   5. (Math.) The difference between the approximate result and
      the true result; -- used particularly in the rule of
      double position.
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   6. (Mensuration)
      (a) The difference between an observed value and the true
          value of a quantity.
      (b) The difference between the observed value of a
          quantity and that which is taken or computed to be the
          true value; -- sometimes called residual error.
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   7. (Law.) A mistake in the proceedings of a court of record
      in matters of law or of fact.
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   8. (Baseball) A fault of a player of the side in the field
      which results in failure to put out a player on the other
      side, or gives him an unearned base.
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   Law of error, or Law of frequency of error (Mensuration),
      the law which expresses the relation between the magnitude
      of an error and the frequency with which that error will
      be committed in making a large number of careful
      measurements of a quantity.

   Probable error. (Mensuration) See under Probable.

   Writ of error (Law), an original writ, which lies after
      judgment in an action at law, in a court of record, to
      correct some alleged error in the proceedings, or in the
      judgment of the court. --Bouvier. Burrill.

   Syn: Mistake; fault; blunder; failure; fallacy; delusion;
        hallucination; sin. See Blunder.
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