Potential Evapo-Transpiration (P E-T) 
The potential, rather than actual, amount of water that might be lost to the atmosphere, by a plant and its soil environment, if an adequate amount of water was continuously available.
Potential Evapo-Transpiration (P E-T)
The potential, rather than actual, amount of water that might be lost to the atmosphere, by a plant and its soil environment, if an adequate amount of water was continuously available.