Final answer:
A milliosmole is 1/1000 of an osmole, which is a unit related to osmolality, used to describe the concentration of solute in a solution, particularly in biological and medical contexts.
Step-by-step explanation:
A milliosmole (mOsm) is 1/1000 of an osmole. This is part of the metric system where the prefix 'milli-' denotes a factor of one thousandth. So, when talking about osmolality in solutions, which measures the number of osmoles of solute per kilogram of solvent, one milliosmole is a thousand times smaller than a single osmole.
Particularly, in biology and medicine, osmolarity and osmolality are important for discussing the concentrations of electrolytes in body fluids which are typically around 280 to 300 mOsm.