well-ordered set A set with a and no infinite descending s. A total ordering "<=" satisfies x <= x; x <= y <= z => x <= z; x <= y <= x => x=y; and for all x, y, x <= y or y <= x. In addition, if a set W is well-ordered then all non-empty subsets A of W have a least element, i.e. there exists x in A such that for all y in A, x <= y. s are es of s, just as s are es of finite sets. (1995-04-19)
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