Basis of a topology
= Basis of a topology
= Open basis
{synonym}
A basis of a topology is a family of open sets such that every open set is a union of members of that family. Equivalently, every point of every open set lies in a basis member contained in it. The rectangles $U\times V$ form a basis for the <product topology> of two spaces. This topological meaning differs from a linear-algebra <basis>.