Weight of a topological space
The smallest cardinal number which is the cardinality of an open base of a topological space. The weight, together with the cardinality, is the most important cardinal invariant of a topological space.
A space satisfies the second axiom of countability if and only if it has countable weight.
|[a1]||A.V. Arkhangel'skii, "Topological function spaces" , Kluwer (1991) (Translated from Russian)|
|[a2]||I. Juhász, "Cardinal functions in topology" , North-Holland (1971)|
|[a3]||Mary Ellen Rudin, Lectures on Set Theoretic Topology, American Mathematical Society (1975) ISBN 0-8218-1673-X Zbl 0318.54001|
Weight of a topological space. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Weight_of_a_topological_space&oldid=42662