Merriam-Webster's Collegiate® Dictionary, 11th Edition
EXPERT
I. adjective
Etymology: Middle English, from Anglo-French & Latin; Anglo-French, from Latin expertus, from past participle of experiri
Date: 14th century
experienced , having, involving, or displaying special skill or knowledge derived from training or experience, see: proficient expertly adverb expertness noun
II. noun
Etymology: Middle French, from expert, adjective
Date: 1535
one with the special skill or knowledge representing mastery of a particular subject,
III. intransitive verb
Date: circa 1889
to serve as an expert