Which is the best definition of efficiency?

The best definition of efficiency is the ability to achieve maximum useful output with minimum wasted input, commonly expressed as the ratio of useful output to total input. In its most universal form, efficiency equals what you get divided by what you put in, often expressed as a percentage, where 100 percent efficiency would mean no waste at all, which is impossible in real systems but serves as an ideal. In physics, efficiency is defined precisely as useful energy output divided by total energy input. In economics, efficiency is defined as allocation of resources that maximizes total value where no one can be made better off without making someone else worse off. In everyday language, the best definition is doing things in the right way without wasting time, money, energy, or effort. What makes this definition best is that it captures three essential elements, first it focuses on results, second it emphasizes minimization of waste, and third it implies maintaining quality, because doing something fast but poorly is not truly efficient. True efficiency balances speed, cost, quality, and resource use to produce the best outcome with the least waste.