Wet bulb temperature is the lowest thermodynamic temperature of air that can be achieved at ambient condition, by creating 100% relative humidity in the immediate surrounding of the thermometer using cotton wick. As Wikipedia says "By contrast, the dew point is the temperature to which the ambient air must be cooled to reach 100% relative humidity assuming there is no evaporation into the air; it is the point where condensate (dew) and rain would form." So I am clear with the definition of both the terms. Now come to the adiabatic saturation process; where I understand how it is a constant enthalpy process; just redistribution of molecules within system. My doubt: (i) What is the difference between dew point and wet bulb temperature; both appears same to me? (ii) In textbooks it is quoted as wet bulb temperature is approximately same as wet bulb temperature; why this approximately term is used. Both should have exactly same, as both have final condition of 100% relative humidity and both are achieved by evaporation of water molecules to the unsaturated air. (iii)Now come to evaporative coolers; say a sand pot, it is also said to be constant wet bulb temperature process, HOW?; Wet bulb temperature is defined at the point where 100% relative humidity is achieved not before same as adiabatic saturation temperature.