<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)
Invariant
·noun An invariable quantity; specifically, a function of the coefficients of one or more forms, which remains unaltered, when these undergo suitable linear transformations.
invariant
¦ adjective never changing.
¦ noun Mathematics a function which remains unchanged when a specified transformation is applied.