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https://english.stackexchange.com/questions/54417/…
"proficient <in/at/with>" What is the correct usage?
With is an instrumental usage, as if English is being considered as a tool -- proficient with knives, proficient with horses, proficient with languages, especially English. Perfectly cromulent, but not often encountered, I suspect. At is a punctual locative, locating some spot in a larger area or metaphoric space (e.g, in May, on Tuesday, at 2:34 pm) -- proficient at getting his deer every ...