 Expander graph

For a finite graph $G=(V,E)$, its edge-expansion constant isAn expander family has uniformly bounded degrees, orders tending to infinity, and expansion constants bounded below by a positive constant.

An **expander graph** is a type of sparse graph that has strong connectivity properties. More formally, it is a family of graphs that exhibit high expansion, meaning that they have a well-defined, large number of edges relative to the number of vertices.