An ordered set is said to be well-ordered if each and every nonempty subset has a smallest or least element. So the well-ordering principle is the following statement: Every nonempty subset S S S of the positive integers has a least element.

How do you prove something is well-ordered?

A set of real numbers is said to be well-ordered if every nonempty subset in it has a smallest element. A well-ordered set must be nonempty and have a smallest element. Having a smallest element does not guarantee that a set of real numbers is well-ordered.

What makes a set well-ordered?

In mathematics, a well-order (or well-ordering or well-order relation) on a set S is a total order on S with the property that every non-empty subset of S has a least element in this ordering. The set S together with the well-order relation is then called a well-ordered set.