Førstetellbarhet
Førstetellbarhet refers to a topological property of a topological space. A topological space X is called first-countable if every point in X has a countable local base. A local base at a point x is a collection of neighborhoods of x such that any neighborhood of x contains at least one neighborhood from the collection.
In simpler terms, for any point in a first-countable space, you can find a countable "collection of
First-countable spaces are common in many areas of mathematics, particularly in analysis and topology. For example,
The property of first-countability is important because it often simplifies proofs and allows for the transfer