Evaporation is water becoming vapour from any surface — a puddle, a lake, wet clothing. Transpiration is the same physical change but specifically water moving through a plant and released as vapour through its leaves. Transpiration is a biological process; evaporation is a purely physical one.
The core difference
The same change of state, distinguished by whether a plant is involved.
- evaporation — liquid water to vapour from any surface.
- transpiration — water drawn up through a plant and released through the stomata in its leaves.
- evapotranspiration — the combined total, which is what hydrologists actually measure.
Why transpiration matters
It is not a side effect. Transpiration is what pulls water up from the roots — evaporation at the leaves creates the tension that drags the whole column upward, which is how water reaches the top of a tall tree without a pump. It also cools the plant.
The combined term
In practice the two are difficult to separate in the field, which is why evapotranspiration exists as a single measured quantity in hydrology and agriculture.
Frequently asked questions
Is transpiration a type of evaporation?
The final step is evaporation, but transpiration describes the whole biological process of water moving through a plant and out through its leaves.
What is evapotranspiration?
The combined total of evaporation and transpiration, used in hydrology because the two are hard to separate in the field.
How does water reach the top of a tall tree?
Evaporation at the leaves creates tension that pulls the water column upward from the roots — the transpiration stream.