Concise: Efficiency is a ratio of time and energy used per objective accomplished.
In-context of human work: Efficiency is the time taken for someone to complete a task successfully, usually with consideration to material, energy, and other resources used in that time.
Ideally: Perfect efficiency optimizes energy and time with satisfactory completion of all required tasks as defined, and compounded with minimization of error* and maximization of production quality. Other notable parameters are affective factors like degree of psychological stress or feeling of ease or accomplishment, other subjective factors including perceived efficiency or impression by employer, and extraneous factors like outside resource use or down-stream effects. *Error includes damage, waste, redundancy, delay or idle, misdirection, and any unnecessary actions.
Take-Away Lesson: Efficiency is far more than just time taken to do something. It is important to note energy and resource use, quality of product and people, as well as complexity and redundancy of actions in that time. Good efficiency often includes using time to collect information, plan, and prepare and always excludes damage or waste, stress or conflict, reversals, and slop or facade. usually we want ideal efficiency so know haste makes waste and thought gets you top spot. Efficiency starts in the mind and works it’s way out exponentially so act wisely asap.