A transition that occurs between a fully-ordered crystalline solid and an isotropic liquid. Mesomorphic transitions can occur (i) from a crystal to a liquid crystal (ii) from a liquid crystal to another liquid crystal and (iii) from a liquid crystal to an isotropic liquid.
See: liquid-crystal transitions
PAC, 1994, 66, 577. 'Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)' on page 586 (https://doi.org/10.1351/pac199466030577)