Evapotranspiration (ET) is the sum of evaporation and plant transpiration.
Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies.
Transpiration accounts for the movement of water within a plant and the subsequent loss of water as vapour through stomata in its leaves.
Evapotranspiration is an important part of the water cycle.
Potential evapotranspiration (PET) is a representation of the environmental demand for evapotranspiration and represents the evapotranspiration rate of a short green crop, completely shading the ground, of uniform height and with adequate water status in the soil profile.
It is a reflection of the energy available to evaporate water, and of the wind available to transport the water vapour from the ground up into the lower atmosphere.
Evapotranspiration is said to equal potential evapotranspiration when there is ample water.
Evapotranspiration is a significant water loss from a watershed.