Raman OH stretching peak frequencies from saturated water vapor decrease by about 20-30 cm(-1) as monomers (OH peak frequency, 3657 cm(-1)) are replaced by dimers (diagnostic frequency less than or equal to 3628-3638 cm(-1))with temperature rise from 298 K to T-c = 647 K. Dimerization increases with temperature in the saturated vapor because of the increase in the pressure/density, and this pressure/density driven dimerization extends into the supercritical fluid until additional polymerization produces trimers, etc., at higher densities. Increasing H-bonding (dimerization) in the saturated vapor equals the decreasing, mainly T-driven, liquid H-bonding when T rises to T-c, where the H-bonding is roughly 17%. This means that the mole fraction of (H2O)(2) molecules X-A. is approximate to 0.7. and the mole fraction of H2O molecules X-B is approximate to 0.3, at the critical point. U-bonding in water at the critical point is not abnormal, because it is essentially independent of die correlation length divergence. The H-bond Delta N of the dimer is discussed.