plural efficiencies
Definition of efficiency
1
: the quality or degree of being efficient
2a
: efficient operation
b(1)
: effective operation as measured by a comparison of production with cost (as in energy, time, and money)
(2)
: the ratio of the useful energy delivered by a dynamic system to the energy supplied to it
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Merriam-Webster unabridged
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Time Traveler for efficiency
The first known use of efficiency was in 1633
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