Second
Summary
A set of second category is a set that is not of first category: in other words a set that is not the union of a countable number of nowhere-dense sets.
An ordinal of the second class is a countable infinite ordinal
An ordinal of the second kind is a limit ordinal or 0
Second order logic allows quantification over subsets as well as over elements of a model
Further reading
- Wikipedia, page 43580500, revision 1360947732, Glossary of set theory, section S. adopted
About this page
| Tag | 4N7H08TX9R |
|---|---|
| URI | m2://4N7H08TX9R |
| Kind | concept |
| Writing | W1 stated |
| Changed | 4 November 2026 |
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What this page needs for W2
- edge defines in: at least one definition (0 of 1)
- edge instance_of in: at least two examples (0 of 2)
- edge not_instance_of in: at least one non-example (0 of 1)
- edge specializes both: the more general notions and the special cases (0 of 1)
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