In mathematics, infinitary combinatorics, or combinatorial set theory, is an extension of ideas in combinatorics to infinite sets. Some of the things studied include continuous graphs and trees, extensions of Ramsey's theorem, and Martin's axiom. Recent developments concern combinatorics of the continuum and combinatorics on successors of singular cardinals.
== Ramsey theory for infinite sets ==
Write κ, λ for ordinals, m for a cardinal number and n for a natural number. Erdős & Rado (1956) introduced the notation
κ
→
(
λ
)
...