A point on a thermodynamic diagram representing the state of the air defined by a pair of variables: P_sat and T_sat, where P_sat is the saturation pressure and T_sat is the saturation temperature. These latter variables are the pressure and temperature of an air parcel that was raised dry- adiabatically or lowered moist-adiabatically until it was just at saturation. The saturation point is a conserved variable for adiabatic motion and thus serves as a tracer for the air parcel on a thermodynamic diagram.