Delta-ring
Sign in to saveIn mathematics, a non-empty collection of sets \mathcal{R} is called a -ring (pronounced "") if it is closed under union, relative complementation, and countable intersection. The name "delta-ring" originates from the German word for intersection, "Durchschnitt", which is meant to highlight the ring's closure under countable intersection, in contrast to a -ring which is closed under countable unions.
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- Definition
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In mathematics, a non-empty collection of sets \mathcal{R} is called a -ring (pronounced "") if it is closed under union, relative complementation, and countable intersection. The name "delta-ring" originates from the German word for intersection, "Durchschnitt", which is meant to highlight the ring's closure under countable intersection, in contrast to a -ring which is closed under countable unions.
== Definition ==