沈殿 (沉淀) refers to the process of sedimentation, where solid particles settle out of a liquid mixture due to gravity. This phenomenon is commonly observed in various natural and industrial processes, such as the formation of sediment in rivers or the separation of components in a mixture. In scientific contexts, 沉淀 is often used in chemistry to describe the formation of a solid precipitate when two solutions react. This process is crucial in fields like environmental science and materials science, where understanding sedimentation can help in water purification and the development of new materials.