*Definition [#hb58748e]
Let X be a topological space.
A subset C is called retrocompact if for every quasi-compact (i.e. [[compact]] but not necessarily Hausdorff) open set U, the intersection of U and C is quasi-compact.

*Reference [#p7fa0965]
Ulrich Gortz and Torsten Wedhorn, ''Algebraic geometry I: schemes with examples and exercises'', Vieweg Teubner Verlag, 2010.