invariant

from WordNet (r) 3.0 (2006)

invariant
    adj 1: unaffected by a designated operation or transformation
    2: unvarying in nature; "maintained a constant temperature";
       "principles of unvarying validity" [syn: {changeless},
       {constant}, {invariant}, {unvarying}]
    n 1: a feature (quantity or property or function) that remains
         unchanged when a particular transformation is applied to it

from The Collaborative International Dictionary of English v.0.48

Invariant \In*va"ri*ant\, n. (Math.)
   An invariable quantity; specifically, a function of the
   coefficients of one or more forms, which remains unaltered,
   when these undergo suitable linear transformations. --J. J.
   Sylvester.
   [1913 Webster]

from The Free On-line Dictionary of Computing (8 July 2008)

invariant

   <programming> A rule, such as the {ordering} of an ordered
   list or {heap}, that applies throughout the life of a data
   structure or procedure.  Each change to the data structure
   must maintain the correctness of the invariant.

   (1996-03-12)

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