(n.) The quality of being proficient in the acquisition of any art, science, or knowledge\; progression in knowledge; improvement; adeptness; as, to acquire proficiency in music.

ability ableness address adeptness adequacy adroitness advancement airmanship all-knowingness anabasis aptitude artfulness artisanship artistry bravura brilliance caliber capability capableness capacity cleverness command competence competency condition control coordination craft craftsmanship cross-disciplinary knowledge cunning deep knowledge deftness dexterity dexterousness dextrousness diplomacy efficacy efficiency encyclopedic knowledge expertise expertness extensive knowledge facility faculty finesse fitness fittedness flair general knowledge genius grace grip handiness headway horsemanship ingeniousness ingenuity knack know-how march marksmanship mastership mastery maturity omniscience ongoing pansophy polyhistory polymathy practical ability preparedness profound knowledge progress prowess qualification quickness readiness resource resourcefulness ripeness savoir faire savoir-faire savvy seamanship seasoning skill skillfulness special knowledge style sufficiency suitability suitableness suitedness susceptibility tact tactfulness talent technical brilliance technical mastery technical skill technique tempering the goods the stuff timing trim virtuosity what it takes wit wizardry workmanship