The analytical composition of a saturated solution, expressed in terms of the proportion of a designated solute in a designated solvent, is the solubility of that solute. The solubility may be expressed as a concentration, molality, mole fraction, mole ratio, etc.
Source:
Orange Book, 2nd ed., p. 84 (https://media.iupac.org/publications/analytical_compendium/)
See also:
PAC, 1990, 62, 2167. 'Glossary of atmospheric chemistry terms (Recommendations 1990)' on page 2214 (https://doi.org/10.1351/pac199062112167)