Given a set S with a partial order <=, an infinite descending chain is a chain V, that is, a subset of S upon which <= defines a total order, such that V has no minimal element, that is, an element m such that for all elements n in V it holds that m <= v.
As an example, in the set of integers, the chain -1,-2,-3,... is an infinite descending chain, but there exists no infinite chain on the natural numbers, every chain of natural numbers has a minimal element.
If a partially ordered set does not contain any infinite descending chains, it is called well-founded. A total ordered set without infinite descending chains is called well-ordered.
