An isolated system is a physical system that does not exchange matter or energy with its surroundings. This means that everything within the system is completely self-contained, allowing for the study of its internal processes without external influences. An example of an isolated system is a thermos bottle that keeps its contents at a constant temperature by preventing heat transfer. In thermodynamics, isolated systems are important for understanding the laws of energy conservation. In such systems, the total energy remains constant over time, as no energy enters or leaves. This concept is crucial in fields like physics and chemistry, where it helps explain phenomena such as entropy and thermodynamic equilibrium.