The conditions of pressure, temperature and composition under which two or more solid phases crystallize at the same time from a single liquid over a finite range of decreasing temperature.
Source:
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 580 (https://doi.org/10.1351/pac199466030577)