expert
n. countablen. someone who has a lot of knowledge or skill in a specific area. You call someone this when they have studied or practiced something for a long time.
n. a person with extensive knowledge or ability based on research, experience, or occupation in a particular field. Often used as a modifier before another noun.
She is an expert in computer programming.
The court called in a medical expert to explain the test results to the jury.
While many claim to understand the market, few are true experts capable of predicting how global political shifts will influence local commodity prices.
Inherited from Middle English [Term?], derived from Old French [Term?] (“experienced”), derived from Latin expertus, perfect active participle of experior (“to try”).
Commonly takes the prepositions 'at', 'in', or 'on' to specify the field of knowledge.
He is expert of historyHe is an expert in historyLearners often use the preposition 'of' instead of the more natural 'in' or 'on' when identifying the subject.