(efficiencies)
1.
Efficiency is the quality of being able to do a task successfully, without wasting time or energy.
There are many ways to increase agricultural ~ in the poorer areas of the world.
...energy ~.
N-UNCOUNT
2.
In physics and engineering, ~ is the ratio between the amount of energy a machine needs to make it work, and the amount it produces. (TECHNICAL)
N-UNCOUNT: also N in pl