the ratio of the output to the input of any system
"The new engine's efficiency improved significantly after the engineers optimized the fuel-to-power conversion ratio."
The extent to which time is well used for the intended task.
"The new software update significantly improved our efficiency by reducing the time needed to generate monthly reports."
In plain English: Efficiency is how well you get something done with the least amount of wasted time or effort.
"The new factory improved efficiency by reducing waste and speeding up production."
Usage: Efficiency describes how well time and resources are used to complete a specific task without waste. Use it when evaluating whether a process achieves its goal with minimal effort or cost.
The word efficiency comes from the Latin noun efficientia, which was formed by combining the root of the English word "efficient" with a suffix meaning "-ness." It entered English as a direct borrowing that retained its original sense of being productive or effective.