Library ▹ Essentials ▹ Numbers ▹ Ordinal numbers
  • Ord (ordinal numbers)
  • (α)
  • ≤
  • Homomorphisms
  • Ordered subsets
  • ≤
  • <
  • Subsets
  • α ≤ β and β ≤ α  ⇔  Iso(α, β) is nonempty  ⇔  α = β  if α, β are ordinal numbers
  • ≤ is a well-order
  • +
  • ⋅
  • Examples
  • |α|
  • finite/infinite
  • countable/uncountable
  • countably infinite
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