Borel map

Symbol-free definition
A Borel map between two topological spaces is a map from one to the other satisfying the following equivalent conditions:


 * The inverse image of every open subset is a Borel subset
 * The inverse image of every closed subset is a Borel subset
 * The inverse image of every Borel subset is a Borel subset

Stronger properties

 * Borel isomorphism
 * Continuous map