= Completely Ramsey-null set
= Completely Ramsey-null
{synonym}
A set $N$ is completely Ramsey-null when every <Ellentuck topology> neighborhood $[s,A]$ has a refinement $[s,B]$ disjoint from $N$, with the same finite stem $s$. Assuming open Ellentuck sets are <completely Ramsey>, every star-<nowhere dense set> is completely Ramsey-null: apply the open-set property to the dense complement of its closure. The <Ellentuck meagre-set fusion lemma> shows that countable unions retain this avoidance property.
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