The definition of efficiency is the ratio of the useful work performed to the total energy expended. It is a measure of how well a system is performing in terms of energy use. Calculating the efficiency of a system is an important part of understanding how it works and how it can be improved. To calculate the efficiency of a system, the amount of energy input must be compared to the amount of useful work output. The efficiency of a system is usually expressed as a percentage, with 100% being the most efficient. By calculating the efficiency of a system, engineers and scientists can determine the best way to use energy and optimize the system for maximum efficiency. Efficiency is an important concept in many areas of engineering and science, and understanding how to calculate it is essential for anyone working in these fields.