Definitions
 closed
1. inaccessible; not open
2. non public (as in closed source)
3. (mathematics)
1. (Topology) a set is closed if its complement is open
2. (Algebra) a set is closed under an operation if the outcome for every argument is also in the set itself. (e.g. $\forall x,y \in Z:\, x + y \in Z$)
Translations:
• Dutch: gesloten (topology), inwendig (algebra)
• French: fermé
• German: abgeschlossen
• Italian: chiuso