Waiver of contract is a voluntary and intentional relinquishment or renunciation of a contract right by some positive act or omission inconsistent with the existence of such right.
The following is an example of a case law referring to waiver of contract:
Forfeiture clauses of a contract may be waived where one party, either by his statements or a course of conduct, leads the other party to believe that he will not insist on forfeiture. It is a general rule that mere indulgence or silence can not be construed as a waiver unless some element of estoppel can be invoked. [Long v. Clark, 90 Kan. 535 (Kan. 1913)].