Absolute neighborhood retract
In mathematics, especially algebraic topology, an absolute neighborhood retract (or ANR) is a "nice" topological space that is considered in homotopy theory; more specifically, in the theory of retracts. For a more general introduction to ANRs, see also Retraction (topology)#Absolute neighborhood retract (ANR).
Source: Wikipedia — Absolute neighborhood retract (CC BY-SA 4.0)