closed set

noun, Mathematics
1.
a set that contains all of its accumulation points, as the set of points on and within a circle; a set having an open set as its complement.
British Dictionary definitions for closed set

closed set

noun (maths)
1.
a set that includes all the values obtained by application of a given operation to its members
2.
(in topological space) a set that contains all its own limit points
closed set in Technology

mathematics
A set S is closed under an operator * if x*y is in S for all x, y in S.
(1994-12-16)