G-delta subset

This article defines a property over pairs of a topological space and a subspace, or equivalently, properties over subspace embeddings (viz, subsets) in topological spaces

Definition

A subset of a topological space is termed a $G_{\delta }$ subset if it is expressible as a countable intersection of open subsets.

Relation with other properties

Stronger properties

• Open subset

Related properties

• F-sigma subset

There are related notions captured in the G hierarchy and F hierarchy