Supercooling

Supercooling is the persistence of a liquid below its freezing point without crystallizing. In water, it occurs when ice nucleation is delayed despite temperatures below 0 °C at standard pressure.

Nucleation: The formation of a stable initial cluster from which a new phase can grow. Supercooled water remains liquid while ice nuclei fail to form or grow.
Freezing rain: Rain that freezes on contact with surfaces at or below 0 °C, forming glaze ice. Its droplets remain liquid below freezing while falling through a cold layer.
Freezing: The phase transition in which a liquid becomes a solid. Freezing ends the liquid state that supercooling temporarily preserves.
Mpemba effect: The observation that initially warmer water can sometimes freeze before initially cooler water under particular conditions. It concerns freezing times rather than the persistence of liquid below the freezing point.
Homogeneous nucleation: Nucleation that begins spontaneously within a uniform material, away from foreign surfaces. It can trigger freezing in exceptionally clean water when thermal fluctuations create an ice embryo.
Cloud physics: The study of cloud formation, structure, and interactions with radiation and precipitation. Supercooled cloud droplets influence how clouds produce ice and precipitation.
Superheating: The persistence of a liquid above its boiling point without boiling. It is the high-temperature metastable counterpart to supercooling.
Wilson cloud chamber: A detector that reveals charged-particle tracks through condensation in a supersaturated vapor. Its expanding chamber can create supercooled water vapor droplets that make particle tracks visible.
Heterogeneous nucleation: Nucleation initiated at a surface, impurity, or other pre-existing interface. Dust and container walls often provide sites that end supercooling by initiating ice.
Rime ice: A rough deposit of ice formed when supercooled cloud droplets freeze on contact with an object. It forms when airborne supercooled droplets crystallize upon striking cold surfaces.

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