Neighbourhood (mathematics)
In topology and related areas of mathematics, a neighbourhood (or neighborhood) is one of the basic concepts in a topological space. Intuitively speaking, a neighbourhood of a point is a set containing the point where you can move that point some amount without leaving the set.
This concept is closely related to the concepts of open set and interior.
Read more about Neighbourhood (mathematics): Definition, In A Metric Space, Examples, Topology From Neighbourhoods, Uniform Neighbourhoods, Punctured Neighbourhood