List of ordinals

Countable ordinals

• 0, the smallest ordinal
• 1, the first successor ordinal
• \( \omega \), the first limit ordinal
• \( \omega^{2} \)
• \( \omega^{3} \)
• \( \omega^{\omega} \)
• \( \psi_{0}(\Omega) = \varphi(1,0) = \varepsilon_{0} \)^{(sort out page)}
• \( \psi_{0}(\Omega^{2}) = \varphi(2,0) = \zeta_{0} \)^{(decide if own page)}
• \( \psi_{0}(\Omega^{\omega}) = \varphi(\omega,0) \)
• \( \psi_{0}(\Omega^{\Omega}) = \varphi(1,0,0) = \Gamma_{0} \), the Feferman-Schutte ordinal and the PTO of ATR₀
• \( \psi_{0}(\Omega^{\Omega^{2}}) = \varphi(1,0,0,0) \), the Ackermann Ordinal^{(decide if keep)}
• \( \psi_{0}(\Omega^{\Omega^{\omega}}) = \varphi(1@\omega) \), the SVO (Small Veblen ordinal)
• \( \psi_{0}(\Omega^{\Omega^{\Omega}}) \), the LVO (Large Veblen ordinal)
• \( \psi_{0}(\Omega_{2}) \), the BHO (Bachmann-Howard ordinal)
• \( \psi_{0}(\Omega_{\omega}) \), the BO (Buchholz ordinal)
• \( \psi_{0}(\varepsilon_{\Omega_{\omega} + 1}) \), the TFB (Takeuti-Feferman-Buchholz ordinal)
• \( \psi_{0}(\Omega_{\Omega_{\dots}}) \), the EBO (Extended Buchholz ordinal)
• \( \psi_{\Omega}(\varepsilon_{I+1}) \), the PTO of KPi
• \( \psi_{\Omega}(\psi_{\chi_{\varepsilon_{M+1}}(0)}(0)) \), the PTO of KPM
• \( \Psi^{0}_{\Omega}(\varepsilon_{K+1}) \), the PTO of KP+\(\Pi_{3}\)-refl.
• \( \psi_\Omega(\varepsilon_{\mathbb{K}+1}) \), the PTO of KP with a \( \Pi_{\mathbb{N}}\)-refl. universe under ZF + V = L
• \( \Psi_{\mathbb{X}}^{\varepsilon_{\Upsilon+1}} \), the limit of Jan-Carl Stegert's second OCF using indescribable cardinals
• PTO of \( \text{Z}_{2} \)
• PTO of \( \text{ZFC} \)
• \( \omega^{\text{CK}}_{1} \)
• RECURSIVE ORDINALS GO HERE^{(sort out)}
• The least recursively inaccessible ordinal^(p.3)
• The least recursively Mahlo ordinal^(p.3)
• The least recursively hyper-Mahlo ordinal^(p.13)
• The least \( \Pi_n \)-reflecting ordinals, for \( 2<n<\omega \)
• The least \( (+1) \)-stable ordinal^(p.4)
• The least \( (^+) \)-stable ordinal = least \( \Pi^1_1 \)-reflecting ordinal^(p.4)
• The least ordinal that is \( \Pi^1_1 \)-reflecting on the \( \Pi^1_1 \)-reflecting ordinals
• The least \( \Sigma^1_1 \)-reflecting ordinal = least non-Gandy ordinal^(pp.3,9)
• The \( (\sigma^1_1)^n \)-reflecting ordinals for \( 1<n<\omega \)^(p.20)
• The least \( (^++1) \)-stable ordinal^{(Is this strictly greater than previous entry?)(p.20)}
• The least doubly \( (+1) \)-stable ordinal^(p.4)
• The least nonprojectible ordinal^(p.5)
• HIGHER STABILITY STUFF GOES HERE^{(sort out)}
• Infinite time Turing machine ordinals
  • \( \lambda \), the supremum of all writable ordinals
  • \( \gamma \), the supremum of all clockable ordinals
  • \( \zeta \), the supremum of all eventually writable ordinals
  • \( \Sigma \), the supremum of all accidentally writable ordinals
• The smallest gap ordinal
• MORE STUFF GOES HERE^{(sort out)}

Uncountable ordinals

• \( \Omega \), the smallest uncountable ordinal
• \( I \), the smallest inaccessible ordinal
• \( M \), the smallest mahlo cardinal
• \( K \), the smallest weakly compact cardinal