The set 
,
where 
is a closed star and 
is a star, is called the link of
in a simplicial complex 
and is denoted 
(Munkres 1993, p. 11).
Simplicial Complex Link
See also
Closed Star, Simplicial Complex, StarExplore with Wolfram|Alpha
References
Munkres, J. R. Elements of Algebraic Topology. New York: Perseus Books Pub., 1993.Referenced on Wolfram|Alpha
Simplicial Complex LinkCite this as:
Weisstein, Eric W. "Simplicial Complex Link." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/SimplicialComplexLink.html