Freezing is a phase transition where a liquid turns into a solid when its temperature is lowered below its freezing point. In accordance with the internationally established definition, freezing means the solidification phase change of a liquid or the liquid content of a substance, usually due to cooling. Although some authors differentiate solidification from freezing as a process where a liquid turns into a solid by increasing the pressure, the two terms are used interchangeably.
For most substances, the melting and freezing points are the same temperature; however, certain substances possess differing solid–liquid transition temperatures. For example, agar displays a hysteresis in its melting point and freezing point. It melts at 85°C (185°F) and solidifies from 32°C to 40°C (89.6°F to 104°F).