Passive systems are designs or technologies that operate without the need for active control or external energy sources. They rely on natural processes to function, such as using sunlight for heating or natural ventilation for cooling. Examples include passive solar heating and green roofs, which utilize the environment to maintain comfortable living conditions. These systems are often more sustainable and cost-effective than active systems, as they require less maintenance and energy input. By harnessing natural resources, passive systems can reduce energy consumption and minimize environmental impact, making them an essential component of sustainable architecture and eco-friendly design.