New posts in Ordinal Numbers

What's the use of countable ordinals? (prompted by a remark of Tim Gowers)

Compact definition of ordinals

Formalizations of The Matchstick Diagram Representation of Ordinals

Do these ordinals exist?

Order type of $\alpha$-computable well-orderings

Is there a modern account of Veblen functions of *several* variables?

Direct axiomatization of ordinal and cardinal numbers

Nice sign-expansions of special surreal numbers

Is there a computable ordinal encoding the proof strength of ZF? Is it knowable?

Surreal numbers, ultrapowers of $\Bbb R$, ordinal-valued functions and the slow-growing hierarchy