User blog comment:Ubersketch/A couple questions./@comment-35470197-20181030234858/@comment-35470197-20181031215136

It roughly means a way to express ordinals \(\alpha\) below a specific ordinal (e.g. \(\Omega\)) by finite strings consisting of letters in a fixed countable set independent of \(\alpha\).

For example, Cantor's normal form gives expressions of ordinals below \(\varepsilon_0\) consisting of four letters 0, ω, +, and ^.