Liquid components of living organisms.
A liquid in the body, e.g. water, blood or semen.
A fluid found in one of the fluid compartments of the body. The principal fluid compartments are intracellular and extracellular. A much smaller segment, the transcellular, includes fluid in the tracheobronchial tree, the gastrointestinal tract, and the bladder; cerebrospinal fluid; and the aqueous humor of the eye. The chemical composition of fluids in the various compartments is carefully regulated. In a normal 154 lb (70 kg) adult human male, 60% of total body weight (i.e., 42 L) is water; in a normal adult female is 55% of total body weight is water (39 L).