a, The phase diagram of water.At only one pressure and temperature can solid, liquid and gaseous water coexist in equilibrium. This triple point defines the Kelvin temperature scale.

These form an entire phase diagram with a triple point. Examining the behavior of the planar free energy, the physicists show, among other things, ...

A triple point separates these two phases and another superfluid phase, the conventional Bose–Einstein condensate, whose coexistence line with the Efimov liquid ends in a critical point.