An '''expert''' is someone who is considered to possess [[knowledge]] and/or [[technique]] in a specialist field of study or activity above that of the average person. Those with great skills and knowledge may be called upon to give testimony in a [[court]] of [[law]] to enable a [[judge]] and/or [[jury]] to determine the veracity of items of evidence.
An '''expert system''' is a [[computer program]] that uses decision-trees evaluate responses from an individual and give [[diagnosis]] or propose a plan of action