A "closed body" refers to a physical structure that is completely enclosed, meaning it has no openings or gaps. This design can be found in various objects, such as containers, vehicles, or even certain types of buildings. The closed nature of these bodies helps to protect their contents from external elements, such as dust, moisture, or contaminants. In engineering and physics, a closed body can also refer to a system where no mass or energy enters or leaves. This concept is important in fields like thermodynamics, where understanding how energy is conserved within a closed body can help in designing efficient systems, such as engines or refrigerators.