Collection of open sets that is sufficient for defining a topology
Also known as topological basis · topological base · basis
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\chi(X)\triangleq\sup\{\chi(x,X)x\in X\} 7 identifiers linking base across the web's reference databases
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In mathematics, a base for the topology of a topological space is a family of open subsets of such that every open set of the topology is equal to the union of some sub-family of . For example, the set of all open intervals in the real number line is a basis for the Euclidean topology on because every open interval is an open set, and also every open subset of can be written as a union of some family of open intervals.