👉 A defining fluid is a substance that is essential for the survival and functioning of living organisms, typically characterized by its unique properties that distinguish it from other fluids. It is often water but can also include other biological fluids like blood, lymph, and cerebrospinal fluid. These fluids serve critical roles in maintaining homeostasis, transporting nutrients, removing waste, and facilitating biochemical reactions necessary for life. They are integral to various physiological processes, including digestion, circulation, and immune response, making them indispensable for the proper functioning of living systems.
