| − | A '''subbasis''' ''S'' for a topology on ''X'' is a collection of subsets of X whose union is ''X''. | + | A '''subbasis''' ''S'' for a topology on ''X'' is a collection of subsets of X whose union is ''X''. The '''topology generated by the subbasis ''S''''' is defined to be the collection ''T'' of all unions of finite intersections of elements in ''S''. |