Invariant

n.

1.

(Math.) An invariable quantity; specifically, a function of the coefficients of one or more forms, which remains unaltered, when these undergo suitable linear transformations.

Adj.	1.	invariant - unaffected by a designated operation or transformation
	2.	invariant - persistent in occurrence and unvarying in nature; "maintained a constant temperature"; "a constant beat"; "principles of unvarying validity"; "a steady breeze" Synonyms: constant, unvarying, changeless, steady

(programming)

invariant - 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.

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