What is the legal difference between laches and waiver?
In legal parlance, laches is a defense which when raised implies the plaintiff caused inordinate delay, was part of the act of which it complains or caused prejudice to a defendant due to any delay. The Statute of Limitations is a common example of laches where a plaintiff is precluded from bringing an action due to inordinate delay.

A defense of waiver claims that the plaintiff knowingly and intentionally signed away, relinquished or otherwise abandoned the right which it claims was violated by the defendant. A common example of a waiver is when one engages in a dangerous act for pleasure such as sky diving or rock climbing. The instructor or facility would have the purchaser sign a waiver for bodily harm suffered from engaging in the dangerous act.

Both defenses are affirmative defenses and must be raised for them to take effect. It is important to note that affirmative defenses can themselves fall to laches and waiver.