An expert is someone who

a. expends the least amount of effort for the greatest skills
b. expends the least amount of efficiency for the greatest practice
c. expends the least amount of energy for the greatest result
d. expends the least amount of experience for the greatest movements

An expert is someone who "expends the least amount of energy for the greatest result".

An expert is somebody who has a prolonged or extraordinary experience through training and instruction in a specific field. Casually, a specialist is somebody generally perceived as a solid wellspring of system or expertise whose staff for judging or choosing appropriately, justly, or astutely is agreed specialist and status by peers or people in general in a particular very much recognized area. An expert, all the more for the most part, is a man with broad learning or capacity in view of research, involvement, or occupation and in a specific region of study. Experts are brought in for exhortation on their individual subject, yet they don't generally concur on the particulars of a field of study.