Exercise 1562Logic, sets and proofs › Countability and cardinalityM1Added 3 Nov 2026
Ordinals vs cardinals
#ordinals#cardinals#distinction
Statement
Explain the difference between ordinals and cardinals.
Hint
Ordinals measure order type; cardinals measure size.
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Solution
Ordinals. Von Neumann ordinals: each ordinal is the set of all smaller ordinals. is the first infinite ordinal; , , , are further ordinals.
Cardinals. Cardinals measure cardinality; , is the first uncountable cardinal.
Distinction. and have the same cardinality () but different order types.
Conclusion. Ordinals refine cardinals with order structure.