"Serous" refers to a type of fluid that is clear, pale yellow, and watery. It is typically found in the body, particularly in the serous membranes, which line body cavities and cover organs. This fluid helps reduce friction between moving organs, such as the heart and lungs, allowing them to function smoothly. In a medical context, "serous" can describe certain types of tissues or conditions. For example, serous cysts are fluid-filled sacs that can develop in various organs. These cysts are usually benign and filled with serous fluid, distinguishing them from other types of cysts that may contain different substances.