A field or algebra of subsets of a set X is a pair (X,F) consisting of the set X and a collection F of subset of X such that
- F is closed under complementation: X∖F∈F for all F∈F;
- F contains the empty set.
- F is closed under binary union (with induction and De Morgan’s laws, this is euqivalent to being closed under binary intersection, finite union, and finite intersection.)
Wikidata ID: Q246506