+A closed system is an arrangement that allows the exchange of [Energy](/wiki/Energy) but not [Matter](/wiki/Matter) with its surroundings. Within its defined [Boundary](/wiki/Boundary), the total mass remains constant, a fundamental concept in [Thermodynamics](/wiki/Thermodynamics).
+## See also
+- [Open System](/wiki/Open_System)
+- [Isolated System](/wiki/Isolated_System)
+- [System Boundary](/wiki/System_Boundary)
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