Efficiency
Etymology
From Latin "efficere" (to accomplish or bring about), from "ex-" (out) and "facere" (to make or do). The root is about producing a result; efficiency narrowed it to producing that result economically. The measurement culture of the industrial age sharpened it into a ratio of output to input.
noun · /ih-FISH-un-see/
Getting the most output from the least input — doing things with minimal waste of time, effort, or resources.
What it names
It isolates the "how well" of work from the "whether it mattered," a split that decides where improvement should even aim.
Example
The factory improved its efficiency by 30 percent — then discovered it was efficiently making a product no one bought.
Related idea
Efficiency is doing things right; effectiveness is doing the right things. As Peter Drucker stressed, you can be flawlessly efficient at the wrong task — and there is nothing so useless as doing efficiently what should not be done at all.