expert
/ˈek-ˌspərt/
noun
one with the special skill or knowledge representing mastery of a particular subject
adjective
having, involving, or displaying special skill or knowledge derived from training or experience
experienced
proficient adept skilled skillful expert mean having great knowledge and experience in a trade or profession. proficient implies a thorough competence derived from training and practice. adept implies special aptitude as well as proficiency.
verb
to serve as an expert