"Subterranean" refers to anything that exists or occurs below the surface of the ground. This term is often used to describe underground environments, such as caves, tunnels, or the soil itself. Subterranean ecosystems can host unique flora and fauna that have adapted to life without sunlight. In addition to natural formations, the term can also apply to human-made structures like subways or mines. These subterranean spaces can serve various purposes, including transportation, resource extraction, or even storage. Understanding subterranean environments is essential for fields like geology, archaeology, and environmental science.