The large kinetic zero-point motion of ⁴He molecules has been properly taken into account in the significant structure theory of liquids in order to describe the liquidity of liquid ⁴He. The Debye and the Bose-Einstein partition functions are used for the solid-like molecules of the normal fluid component and for the whole gas-like molecules, respectively. The solid-like molecules of the superfluid component are considered as ground state molecules without having positional degeneracies. The Bragg-Williams approximation of an order/disorder phase transition has been applied to the λ transition of liquid ⁴He. Thermodynamic and surface properties of liquid ⁴He have been calculated up to the critical point. The results are satisfactory when compared with the observed values.