The process of transferring a dissolved substance from one liquid phase to another (immiscible or partially miscible) liquid phase in contact with it. Although extraction, partition and distribution are not synonymous, extraction may replace distribution where appropriate.
Sources:
Orange Book, 2nd ed., p. 87 (https://media.iupac.org/publications/analytical_compendium/)
PAC, 1993, 65, 2373. 'Nomenclature for liquid-liquid distribution (solvent extraction) (IUPAC Recommendations 1993)' on page 2378 (https://doi.org/10.1351/pac199365112373)