The Lambda point refers to a specific temperature at which helium transitions from a normal fluid phase to a superfluid phase. This occurs at around 2.17 Kelvin (K) for helium-4, one of the isotopes of helium. At the Lambda point, the specific heat capacity of helium-4 diverges, which is indicative of a phase transition.
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The lambda point is the temperature of the transition between ordinary liquid helium-4 and its superfluid phase, named after the sharp lambda-shaped heat capacity feature. At saturated vapor pressure it lies near . Its value varies with pressure.