nth order phase transition

A transition in which the molar Gibbs energy (or chemical potential) and its $( n − 1 )$ th-order derivatives are continuous, whereas the $n$ th-order derivatives with respect to temperature and pressure are discontinuous at the transition point.

See: first-order transition, second-order transition

Source:

PAC, 1994, 66, 577 (Definitions of terms relating to phase transitions of the solid state (IUPAC Recommendations 1994)) on page 587