Borel field of sets
family of Borel sets, generated by a system of sets $M$
The smallest system of sets containing $M$ and closed with respect to the operations of countable union and taking complements (see also $\sigma$-algebra.
Borel field of sets. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Borel_field_of_sets&oldid=27188