Question

Latent heat of fusion

Answer 1

the amount of heat required to change a unit mass of a liquid at its boilling point in to vapour without an increase in temperature

Answer 2

Latent heat of fusion is the amount of heat energy that is required by ice to melt into water, at that constant temperature.  Latent heat is the change in the enthalpy of a solid when it is heated at the constant temperature of melting point to become liquid.  It is measured in Joules/gm or KJ/kg. 

Latent heat of fusion is the amount of heat that is released by water (liquid) when it freezes to form (solid) ice, at that constant temperature.

For both processes melting or freezing the amount of heat involved is same.

For water it is equal to  334 Joules/gm at  0 deg C.