A stack 
on a topological space 
is said to be a stack of groupoids if for each open subset 
, the category 
is a groupoid.
Stack of Groupoids
See also
Algebraic Geometry Stack, Category, Category Theory, Groupoid, Topological SpaceThis entry contributed by Christopher Stover
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References
Moerdijk, I. "Introduction to the Language of Stacks and Gerbes." 2002. http://arxiv.org/abs/math/0212266.Cite this as:
Stover, Christopher. "Stack of Groupoids." From MathWorld--A Wolfram Web Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/StackofGroupoids.html