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2. Ordinal number - Wikipedia

   en.wikipedia.org/wiki/Ordinal_number

   Cantor's work with derived sets and ordinal numbers led to the Cantor-Bendixson theorem. [14] Using successors, limits, and cardinality, Cantor generated an unbounded sequence of ordinal numbers and number classes. [15] The (α + 1)-th number class is the set of ordinals whose predecessors form a set of the same cardinality as the α-th

3. Epsilon number - Wikipedia

   en.wikipedia.org/wiki/Epsilon_number

   The standard definition of ordinal exponentiation with base α is: =, =, when has an immediate predecessor . = {< <}, whenever is a limit ordinal. From this definition, it follows that for any fixed ordinal α > 1, the mapping is a normal function, so it has arbitrarily large fixed points by the fixed-point lemma for normal functions.

4. List of types of numbers - Wikipedia

   en.wikipedia.org/wiki/List_of_types_of_numbers

   Ordinal numbers: Finite and infinite numbers used to describe the order type of well-ordered sets. Cardinal numbers : Finite and infinite numbers used to describe the cardinalities of sets . Infinitesimals : These are smaller than any positive real number, but are nonetheless greater than zero.

5. Even and odd ordinals - Wikipedia

   en.wikipedia.org/wiki/Even_and_odd_ordinals

   In fact, the even ordinal ω + 4 cannot be expressed as β + β, and the ordinal number (ω + 3)2 = (ω + 3) + (ω + 3) = ω + (3 + ω) + 3 = ω + ω + 3 = ω2 + 3. is not even. A simple application of ordinal parity is the idempotence law for cardinal addition (given the well-ordering theorem). Given an infinite cardinal κ, or generally any ...

6. Ordinal arithmetic - Wikipedia

   en.wikipedia.org/wiki/Ordinal_arithmetic

   The equation 2 ω = ω expresses the fact that finite sequences of zeros and ones can be identified with natural numbers, using the binary number system. The ordinal ω ω can be viewed as the order type of finite sequences of natural numbers; every element of ω ω (i.e. every ordinal smaller than ω ω) can be uniquely written in the form ...

7. Von Neumann cardinal assignment - Wikipedia

   en.wikipedia.org/wiki/Von_Neumann_cardinal...

   The von Neumann cardinal assignment is a cardinal assignment that uses ordinal numbers.For a well-orderable set U, we define its cardinal number to be the smallest ordinal number equinumerous to U, using the von Neumann definition of an ordinal number.