In the pheesical sciences, a phase is a region o space (a thermodynamic seestem), throughoot which aw pheesical properties o a material are essentially uniform. Examples o pheesical properties include density, index o refraction, magnetization an chemical composeetion. A simple description is that a phase is a region o material that is chemically uniform, pheesically distinct, an (eften) mechanically separable. In a seestem consistin o ice an watter in a glass jar, the ice cubes are ane phase, the watter is a seicont phase, an the humid air ower the watter is a third phase. The glass o the jar is anither separate phase.