Rarified space

This article defines a property of topological spaces: a property that can be evaluated to true/false for any topological space|View a complete list of properties of topological spaces

Definition

A topological space is termed a rarified space or a $\lambda$-space if every countable subset of it is a $G_{\delta }$-[G-delta subset|subset]], viz a countable intersection of open subsets.

Relation with other properties

Stronger properties

• Discrete space
• Q-set space