A standard Psychrometric Chart graphically presents the thermodynamic properties of moist air at a fixed atmospheric pressure:
Properties plotted and directly readable include: Dry bulb temperature, Wet bulb temperature, Dew point temperature (A), Relative humidity, Specific humidity / humidity ratio (D), Humid volume (C), and Enthalpy.
In contrast, the Triple point (B) of water is a specific fundamental thermodynamic state point (0.01°C, 611.7 Pa) located on a general pressure-temperature phase diagram of pure water, NOT a variable property plotted on psychrometric charts.